path: root/Documentation/powerpc/booting-without-of.txt

           Booting the Linux/ppc kernel without Open Firmware
           --------------------------------------------------

(c) 2005 Benjamin Herrenschmidt <benh at kernel.crashing.org>,
    IBM Corp.
(c) 2005 Becky Bruce <becky.bruce at freescale.com>,
    Freescale Semiconductor, FSL SOC and 32-bit additions
(c) 2006 MontaVista Software, Inc.
    Flash chip node definition

Table of Contents
=================

  I - Introduction
    1) Entry point for arch/powerpc
    2) Board support

  II - The DT block format
    1) Header
    2) Device tree generalities
    3) Device tree "structure" block
    4) Device tree "strings" block

  III - Required content of the device tree
    1) Note about cells and address representation
    2) Note about "compatible" properties
    3) Note about "name" properties
    4) Note about node and property names and character set
    5) Required nodes and properties
      a) The root node
      b) The /cpus node
      c) The /cpus/* nodes
      d) the /memory node(s)
      e) The /chosen node
      f) the /soc<SOCname> node

  IV - "dtc", the device tree compiler

  V - Recommendations for a bootloader

  VI - System-on-a-chip devices and nodes
    1) Defining child nodes of an SOC
    2) Representing devices without a current OF specification
      a) MDIO IO device
      b) Gianfar-compatible ethernet nodes
      c) PHY nodes
      d) Interrupt controllers
      e) I2C
      f) Freescale SOC USB controllers
      g) Freescale SOC SEC Security Engines
      h) Board Control and Status (BCSR)
      i) Freescale QUICC Engine module (QE)
      j) CFI or JEDEC memory-mapped NOR flash
      k) Global Utilities Block
      l) Freescale Communications Processor Module
      m) Chipselect/Local Bus
      n) 4xx/Axon EMAC ethernet nodes
      o) Xilinx IP cores
      p) Freescale Synchronous Serial Interface
	  q) USB EHCI controllers

  VII - Specifying interrupt information for devices
    1) interrupts property
    2) interrupt-parent property
    3) OpenPIC Interrupt Controllers
    4) ISA Interrupt Controllers

  Appendix A - Sample SOC node for MPC8540


Revision Information
====================

   May 18, 2005: Rev 0.1 - Initial draft, no chapter III yet.

   May 19, 2005: Rev 0.2 - Add chapter III and bits & pieces here or
                           clarifies the fact that a lot of things are
                           optional, the kernel only requires a very
                           small device tree, though it is encouraged
                           to provide an as complete one as possible.

   May 24, 2005: Rev 0.3 - Precise that DT block has to be in RAM
			 - Misc fixes
			 - Define version 3 and new format version 16
			   for the DT block (version 16 needs kernel
			   patches, will be fwd separately).
			   String block now has a size, and full path
			   is replaced by unit name for more
			   compactness.
			   linux,phandle is made optional, only nodes
			   that are referenced by other nodes need it.
			   "name" property is now automatically
			   deduced from the unit name

   June 1, 2005: Rev 0.4 - Correct confusion between OF_DT_END and
                           OF_DT_END_NODE in structure definition.
                         - Change version 16 format to always align
                           property data to 4 bytes. Since tokens are
                           already aligned, that means no specific
                           required alignment between property size
                           and property data. The old style variable
                           alignment would make it impossible to do
                           "simple" insertion of properties using
                           memmove (thanks Milton for
                           noticing). Updated kernel patch as well
			 - Correct a few more alignment constraints
			 - Add a chapter about the device-tree
                           compiler and the textural representation of
                           the tree that can be "compiled" by dtc.

   November 21, 2005: Rev 0.5
			 - Additions/generalizations for 32-bit
			 - Changed to reflect the new arch/powerpc
			   structure
			 - Added chapter VI


 ToDo:
	- Add some definitions of interrupt tree (simple/complex)
	- Add some definitions for PCI host bridges
	- Add some common address format examples
	- Add definitions for standard properties and "compatible"
	  names for cells that are not already defined by the existing
	  OF spec.
	- Compare FSL SOC use of PCI to standard and make sure no new
	  node definition required.
	- Add more information about node definitions for SOC devices
  	  that currently have no standard, like the FSL CPM.


I - Introduction
================

During the recent development of the Linux/ppc64 kernel, and more
specifically, the addition of new platform types outside of the old
IBM pSeries/iSeries pair, it was decided to enforce some strict rules
regarding the kernel entry and bootloader <-> kernel interfaces, in
order to avoid the degeneration that had become the ppc32 kernel entry
point and the way a new platform should be added to the kernel. The
legacy iSeries platform breaks those rules as it predates this scheme,
but no new board support will be accepted in the main tree that
doesn't follows them properly.  In addition, since the advent of the
arch/powerpc merged architecture for ppc32 and ppc64, new 32-bit
platforms and 32-bit platforms which move into arch/powerpc will be
required to use these rules as well.

The main requirement that will be defined in more detail below is
the presence of a device-tree whose format is defined after Open
Firmware specification. However, in order to make life easier
to embedded board vendors, the kernel doesn't require the device-tree
to represent every device in the system and only requires some nodes
and properties to be present. This will be described in detail in
section III, but, for example, the kernel does not require you to
create a node for every PCI device in the system. It is a requirement
to have a node for PCI host bridges in order to provide interrupt
routing informations and memory/IO ranges, among others. It is also
recommended to define nodes for on chip devices and other busses that
don't specifically fit in an existing OF specification. This creates a
great flexibility in the way the kernel can then probe those and match
drivers to device, without having to hard code all sorts of tables. It
also makes it more flexible for board vendors to do minor hardware
upgrades without significantly impacting the kernel code or cluttering
it with special cases.


1) Entry point for arch/powerpc
-------------------------------

   There is one and one single entry point to the kernel, at the start
   of the kernel image. That entry point supports two calling
   conventions:

        a) Boot from Open Firmware. If your firmware is compatible
        with Open Firmware (IEEE 1275) or provides an OF compatible
        client interface API (support for "interpret" callback of
        forth words isn't required), you can enter the kernel with:

              r5 : OF callback pointer as defined by IEEE 1275
              bindings to powerpc. Only the 32-bit client interface
              is currently supported

              r3, r4 : address & length of an initrd if any or 0

              The MMU is either on or off; the kernel will run the
              trampoline located in arch/powerpc/kernel/prom_init.c to
              extract the device-tree and other information from open
              firmware and build a flattened device-tree as described
              in b). prom_init() will then re-enter the kernel using
              the second method. This trampoline code runs in the
              context of the firmware, which is supposed to handle all
              exceptions during that time.

        b) Direct entry with a flattened device-tree block. This entry
        point is called by a) after the OF trampoline and can also be
        called directly by a bootloader that does not support the Open
        Firmware client interface. It is also used by "kexec" to
        implement "hot" booting of a new kernel from a previous
        running one. This method is what I will describe in more
        details in this document, as method a) is simply standard Open
        Firmware, and thus should be implemented according to the
        various standard documents defining it and its binding to the
        PowerPC platform. The entry point definition then becomes:

                r3 : physical pointer to the device-tree block
                (defined in chapter II) in RAM

                r4 : physical pointer to the kernel itself. This is
                used by the assembly code to properly disable the MMU
                in case you are entering the kernel with MMU enabled
                and a non-1:1 mapping.

                r5 : NULL (as to differentiate with method a)

        Note about SMP entry: Either your firmware puts your other
        CPUs in some sleep loop or spin loop in ROM where you can get
        them out via a soft reset or some other means, in which case
        you don't need to care, or you'll have to enter the kernel
        with all CPUs. The way to do that with method b) will be
        described in a later revision of this document.


2) Board support
----------------

64-bit kernels:

   Board supports (platforms) are not exclusive config options. An
   arbitrary set of board supports can be built in a single kernel
   image. The kernel will "know" what set of functions to use for a
   given platform based on the content of the device-tree. Thus, you
   should:

        a) add your platform support as a _boolean_ option in
        arch/powerpc/Kconfig, following the example of PPC_PSERIES,
        PPC_PMAC and PPC_MAPLE. The later is probably a good
        example of a board support to start from.

        b) create your main platform file as
        "arch/powerpc/platforms/myplatform/myboard_setup.c" and add it
        to the Makefile under the condition of your CONFIG_
        option. This file will define a structure of type "ppc_md"
        containing the various callbacks that the generic code will
        use to get to your platform specific code

        c) Add a reference to your "ppc_md" structure in the
        "machines" table in arch/powerpc/kernel/setup_64.c if you are
        a 64-bit platform.

        d) request and get assigned a platform number (see PLATFORM_*
        constants in include/asm-powerpc/processor.h

32-bit embedded kernels:

  Currently, board support is essentially an exclusive config option.
  The kernel is configured for a single platform.  Part of the reason
  for this is to keep kernels on embedded systems small and efficient;
  part of this is due to the fact the code is already that way. In the
  future, a kernel may support multiple platforms, but only if the
  platforms feature the same core architecture.  A single kernel build
  cannot support both configurations with Book E and configurations
  with classic Powerpc architectures.

  32-bit embedded platforms that are moved into arch/powerpc using a
  flattened device tree should adopt the merged tree practice of
  setting ppc_md up dynamically, even though the kernel is currently
  built with support for only a single platform at a time.  This allows
  unification of the setup code, and will make it easier to go to a
  multiple-platform-support model in the future.

NOTE: I believe the above will be true once Ben's done with the merge
of the boot sequences.... someone speak up if this is wrong!

  To add a 32-bit embedded platform support, follow the instructions
  for 64-bit platforms above, with the exception that the Kconfig
  option should be set up such that the kernel builds exclusively for
  the platform selected.  The processor type for the platform should
  enable another config option to select the specific board
  supported.

NOTE: If Ben doesn't merge the setup files, may need to change this to
point to setup_32.c


   I will describe later the boot process and various callbacks that
   your platform should implement.


II - The DT block format
========================


This chapter defines the actual format of the flattened device-tree
passed to the kernel. The actual content of it and kernel requirements
are described later. You can find example of code manipulating that
format in various places, including arch/powerpc/kernel/prom_init.c
which will generate a flattened device-tree from the Open Firmware
representation, or the fs2dt utility which is part of the kexec tools
which will generate one from a filesystem representation. It is
expected that a bootloader like uboot provides a bit more support,
that will be discussed later as well.

Note: The block has to be in main memory. It has to be accessible in
both real mode and virtual mode with no mapping other than main
memory. If you are writing a simple flash bootloader, it should copy
the block to RAM before passing it to the kernel.


1) Header
---------

   The kernel is entered with r3 pointing to an area of memory that is
   roughly described in include/asm-powerpc/prom.h by the structure
   boot_param_header:

struct boot_param_header {
        u32     magic;                  /* magic word OF_DT_HEADER */
        u32     totalsize;              /* total size of DT block */
        u32     off_dt_struct;          /* offset to structure */
        u32     off_dt_strings;         /* offset to strings */
        u32     off_mem_rsvmap;         /* offset to memory reserve map
                                           */
        u32     version;                /* format version */
        u32     last_comp_version;      /* last compatible version */

        /* version 2 fields below */
        u32     boot_cpuid_phys;        /* Which physical CPU id we're
                                           booting on */
        /* version 3 fields below */
        u32     size_dt_strings;        /* size of the strings block */

        /* version 17 fields below */
        u32	size_dt_struct;		/* size of the DT structure block */
};

   Along with the constants:

/* Definitions used by the flattened device tree */
#define OF_DT_HEADER            0xd00dfeed      /* 4: version,
						   4: total size */
#define OF_DT_BEGIN_NODE        0x1             /* Start node: full name
						   */
#define OF_DT_END_NODE          0x2             /* End node */
#define OF_DT_PROP              0x3             /* Property: name off,
                                                   size, content */
#define OF_DT_END               0x9

   All values in this header are in big endian format, the various
   fields in this header are defined more precisely below. All
   "offset" values are in bytes from the start of the header; that is
   from the value of r3.

   - magic

     This is a magic value that "marks" the beginning of the
     device-tree block header. It contains the value 0xd00dfeed and is
     defined by the constant OF_DT_HEADER

   - totalsize

     This is the total size of the DT block including the header. The
     "DT" block should enclose all data structures defined in this
     chapter (who are pointed to by offsets in this header). That is,
     the device-tree structure, strings, and the memory reserve map.

   - off_dt_struct

     This is an offset from the beginning of the header to the start
     of the "structure" part the device tree. (see 2) device tree)

   - off_dt_strings

     This is an offset from the beginning of the header to the start
     of the "strings" part of the device-tree

   - off_mem_rsvmap

     This is an offset from the beginning of the header to the start
     of the reserved memory map. This map is a list of pairs of 64-
     bit integers. Each pair is a physical address and a size. The
     list is terminated by an entry of size 0. This map provides the
     kernel with a list of physical memory areas that are "reserved"
     and thus not to be used for memory allocations, especially during
     early initialization. The kernel needs to allocate memory during
     boot for things like un-flattening the device-tree, allocating an
     MMU hash table, etc... Those allocations must be done in such a
     way to avoid overriding critical things like, on Open Firmware
     capable machines, the RTAS instance, or on some pSeries, the TCE
     tables used for the iommu. Typically, the reserve map should
     contain _at least_ this DT block itself (header,total_size). If
     you are passing an initrd to the kernel, you should reserve it as
     well. You do not need to reserve the kernel image itself. The map
     should be 64-bit aligned.

   - version

     This is the version of this structure. Version 1 stops
     here. Version 2 adds an additional field boot_cpuid_phys.
     Version 3 adds the size of the strings block, allowing the kernel
     to reallocate it easily at boot and free up the unused flattened
     structure after expansion. Version 16 introduces a new more
     "compact" format for the tree itself that is however not backward
     compatible. Version 17 adds an additional field, size_dt_struct,
     allowing it to be reallocated or moved more easily (this is
     particularly useful for bootloaders which need to make
     adjustments to a device tree based on probed information). You
     should always generate a structure of the highest version defined
     at the time of your implementation. Currently that is version 17,
     unless you explicitly aim at being backward compatible.

   - last_comp_version

     Last compatible version. This indicates down to what version of
     the DT block you are backward compatible. For example, version 2
     is backward compatible with version 1 (that is, a kernel build
     for version 1 will be able to boot with a version 2 format). You
     should put a 1 in this field if you generate a device tree of
     version 1 to 3, or 16 if you generate a tree of version 16 or 17
     using the new unit name format.

   - boot_cpuid_phys

     This field only exist on version 2 headers. It indicate which
     physical CPU ID is calling the kernel entry point. This is used,
     among others, by kexec. If you are on an SMP system, this value
     should match the content of the "reg" property of the CPU node in
     the device-tree corresponding to the CPU calling the kernel entry
     point (see further chapters for more informations on the required
     device-tree contents)

   - size_dt_strings

     This field only exists on version 3 and later headers.  It
     gives the size of the "strings" section of the device tree (which
     starts at the offset given by off_dt_strings).

   - size_dt_struct

     This field only exists on version 17 and later headers.  It gives
     the size of the "structure" section of the device tree (which
     starts at the offset given by off_dt_struct).

   So the typical layout of a DT block (though the various parts don't
   need to be in that order) looks like this (addresses go from top to
   bottom):


             ------------------------------
       r3 -> |  struct boot_param_header  |
             ------------------------------
             |      (alignment gap) (*)   |
             ------------------------------
             |      memory reserve map    |
             ------------------------------
             |      (alignment gap)       |
             ------------------------------
             |                            |
             |    device-tree structure   |
             |                            |
             ------------------------------
             |      (alignment gap)       |
             ------------------------------
             |                            |
             |     device-tree strings    |
             |                            |
      -----> ------------------------------
      |
      |
      --- (r3 + totalsize)

  (*) The alignment gaps are not necessarily present; their presence
      and size are dependent on the various alignment requirements of
      the individual data blocks.


2) Device tree generalities
---------------------------

This device-tree itself is separated in two different blocks, a
structure block and a strings block. Both need to be aligned to a 4
byte boundary.

First, let's quickly describe the device-tree concept before detailing
the storage format. This chapter does _not_ describe the detail of the
required types of nodes & properties for the kernel, this is done
later in chapter III.

The device-tree layout is strongly inherited from the definition of
the Open Firmware IEEE 1275 device-tree. It's basically a tree of
nodes, each node having two or more named properties. A property can
have a value or not.

It is a tree, so each node has one and only one parent except for the
root node who has no parent.

A node has 2 names. The actual node name is generally contained in a
property of type "name" in the node property list whose value is a
zero terminated string and is mandatory for version 1 to 3 of the
format definition (as it is in Open Firmware). Version 16 makes it
optional as it can generate it from the unit name defined below.

There is also a "unit name" that is used to differentiate nodes with
the same name at the same level, it is usually made of the node
names, the "@" sign, and a "unit address", which definition is
specific to the bus type the node sits on.

The unit name doesn't exist as a property per-se but is included in
the device-tree structure. It is typically used to represent "path" in
the device-tree. More details about the actual format of these will be
below.

The kernel powerpc generic code does not make any formal use of the
unit address (though some board support code may do) so the only real
requirement here for the unit address is to ensure uniqueness of
the node unit name at a given level of the tree. Nodes with no notion
of address and no possible sibling of the same name (like /memory or
/cpus) may omit the unit address in the context of this specification,
or use the "@0" default unit address. The unit name is used to define
a node "full path", which is the concatenation of all parent node
unit names separated with "/".

The root node doesn't have a defined name, and isn't required to have
a name property either if you are using version 3 or earlier of the
format. It also has no unit address (no @ symbol followed by a unit
address). The root node unit name is thus an empty string. The full
path to the root node is "/".

Every node which actually represents an actual device (that is, a node
which isn't only a virtual "container" for more nodes, like "/cpus"
is) is also required to have a "device_type" property indicating the
type of node .

Finally, every node that can be referenced from a property in another
node is required to have a "linux,phandle" property. Real open
firmware implementations provide a unique "phandle" value for every
node that the "prom_init()" trampoline code turns into
"linux,phandle" properties. However, this is made optional if the
flattened device tree is used directly. An example of a node
referencing another node via "phandle" is when laying out the
interrupt tree which will be described in a further version of this
document.

This "linux, phandle" property is a 32-bit value that uniquely
identifies a node. You are free to use whatever values or system of
values, internal pointers, or whatever to generate these, the only
requirement is that every node for which you provide that property has
a unique value for it.

Here is an example of a simple device-tree. In this example, an "o"
designates a node followed by the node unit name. Properties are
presented with their name followed by their content. "content"
represents an ASCII string (zero terminated) value, while <content>
represents a 32-bit hexadecimal value. The various nodes in this
example will be discussed in a later chapter. At this point, it is
only meant to give you a idea of what a device-tree looks like. I have
purposefully kept the "name" and "linux,phandle" properties which
aren't necessary in order to give you a better idea of what the tree
looks like in practice.

  / o device-tree
      |- name = "device-tree"
      |- model = "MyBoardName"
      |- compatible = "MyBoardFamilyName"
      |- #address-cells = <2>
      |- #size-cells = <2>
      |- linux,phandle = <0>
      |
      o cpus
      | | - name = "cpus"
      | | - linux,phandle = <1>
      | | - #address-cells = <1>
      | | - #size-cells = <0>
      | |
      | o PowerPC,970@0
      |   |- name = "PowerPC,970"
      |   |- device_type = "cpu"
      |   |- reg = <0>
      |   |- clock-frequency = <5f5e1000>
      |   |- 64-bit
      |   |- linux,phandle = <2>
      |
      o memory@0
      | |- name = "memory"
      | |- device_type = "memory"
      | |- reg = <00000000 00000000 00000000 20000000>
      | |- linux,phandle = <3>
      |
      o chosen
        |- name = "chosen"
        |- bootargs = "root=/dev/sda2"
        |- linux,phandle = <4>

This tree is almost a minimal tree. It pretty much contains the
minimal set of required nodes and properties to boot a linux kernel;
that is, some basic model informations at the root, the CPUs, and the
physical memory layout.  It also includes misc information passed
through /chosen, like in this example, the platform type (mandatory)
and the kernel command line arguments (optional).

The /cpus/PowerPC,970@0/64-bit property is an example of a
property without a value. All other properties have a value. The
significance of the #address-cells and #size-cells properties will be
explained in chapter IV which defines precisely the required nodes and
properties and their content.


3) Device tree "structure" block

The structure of the device tree is a linearized tree structure. The
"OF_DT_BEGIN_NODE" token starts a new node, and the "OF_DT_END_NODE"
ends that node definition. Child nodes are simply defined before
"OF_DT_END_NODE" (that is nodes within the node). A 'token' is a 32
bit value. The tree has to be "finished" with a OF_DT_END token

Here's the basic structure of a single node:

     * token OF_DT_BEGIN_NODE (that is 0x00000001)
     * for version 1 to 3, this is the node full path as a zero
       terminated string, starting with "/". For version 16 and later,
       this is the node unit name only (or an empty string for the
       root node)
     * [align gap to next 4 bytes boundary]
     * for each property:
        * token OF_DT_PROP (that is 0x00000003)
        * 32-bit value of property value size in bytes (or 0 if no
          value)
        * 32-bit value of offset in string block of property name
        * property value data if any
        * [align gap to next 4 bytes boundary]
     * [child nodes if any]
     * token OF_DT_END_NODE (that is 0x00000002)

So the node content can be summarized as a start token, a full path,
a list of properties, a list of child nodes, and an end token. Every
child node is a full node structure itself as defined above.

NOTE: The above definition requires that all property definitions for
a particular node MUST precede any subnode definitions for that node.
Although the structure would not be ambiguous if properties and
subnodes were intermingled, the kernel parser requires that the
properties come first (up until at least 2.6.22).  Any tools
manipulating a flattened tree must take care to preserve this
constraint.

4) Device tree "strings" block

In order to save space, property names, which are generally redundant,
are stored separately in the "strings" block. This block is simply the
whole bunch of zero terminated strings for all property names
concatenated together. The device-tree property definitions in the
structure block will contain offset values from the beginning of the
strings block.


III - Required content of the device tree
=========================================

WARNING: All "linux,*" properties defined in this document apply only
to a flattened device-tree. If your platform uses a real
implementation of Open Firmware or an implementation compatible with
the Open Firmware client interface, those properties will be created
by the trampoline code in the kernel's prom_init() file. For example,
that's where you'll have to add code to detect your board model and
set the platform number. However, when using the flattened device-tree
entry point, there is no prom_init() pass, and thus you have to
provide those properties yourself.


1) Note about cells and address representation
----------------------------------------------

The general rule is documented in the various Open Firmware
documentations. If you choose to describe a bus with the device-tree
and there exist an OF bus binding, then you should follow the
specification. However, the kernel does not require every single
device or bus to be described by the device tree.

In general, the format of an address for a device is defined by the
parent bus type, based on the #address-cells and #size-cells
properties.  Note that the parent's parent definitions of #address-cells
and #size-cells are not inhereted so every node with children must specify
them.  The kernel requires the root node to have those properties defining
addresses format for devices directly mapped on the processor bus.

Those 2 properties define 'cells' for representing an address and a
size. A "cell" is a 32-bit number. For example, if both contain 2
like the example tree given above, then an address and a size are both
composed of 2 cells, and each is a 64-bit number (cells are
concatenated and expected to be in big endian format). Another example
is the way Apple firmware defines them, with 2 cells for an address
and one cell for a size.  Most 32-bit implementations should define
#address-cells and #size-cells to 1, which represents a 32-bit value.
Some 32-bit processors allow for physical addresses greater than 32
bits; these processors should define #address-cells as 2.

"reg" properties are always a tuple of the type "address size" where
the number of cells of address and size is specified by the bus
#address-cells and #size-cells. When a bus supports various address
spaces and other flags relative to a given address allocation (like
prefetchable, etc...) those flags are usually added to the top level
bits of the physical address. For example, a PCI physical address is
made of 3 cells, the bottom two containing the actual address itself
while the top cell contains address space indication, flags, and pci
bus & device numbers.

For busses that support dynamic allocation, it's the accepted practice
to then not provide the address in "reg" (keep it 0) though while
providing a flag indicating the address is dynamically allocated, and
then, to provide a separate "assigned-addresses" property that
contains the fully allocated addresses. See the PCI OF bindings for
details.

In general, a simple bus with no address space bits and no dynamic
allocation is preferred if it reflects your hardware, as the existing
kernel address parsing functions will work out of the box. If you
define a bus type with a more complex address format, including things
like address space bits, you'll have to add a bus translator to the
prom_parse.c file of the recent kernels for your bus type.

The "reg" property only defines addresses and sizes (if #size-cells is
non-0) within a given bus. In order to translate addresses upward
(that is into parent bus addresses, and possibly into CPU physical
addresses), all busses must contain a "ranges" property. If the
"ranges" property is missing at a given level, it's assumed that
translation isn't possible, i.e., the registers are not visible on the
parent bus.  The format of the "ranges" property for a bus is a list
of:

	bus address, parent bus address, size

"bus address" is in the format of the bus this bus node is defining,
that is, for a PCI bridge, it would be a PCI address. Thus, (bus
address, size) defines a range of addresses for child devices. "parent
bus address" is in the format of the parent bus of this bus. For
example, for a PCI host controller, that would be a CPU address. For a
PCI<->ISA bridge, that would be a PCI address. It defines the base
address in the parent bus where the beginning of that range is mapped.

For a new 64-bit powerpc board, I recommend either the 2/2 format or
Apple's 2/1 format which is slightly more compact since sizes usually
fit in a single 32-bit word.   New 32-bit powerpc boards should use a
1/1 format, unless the processor supports physical addresses greater
than 32-bits, in which case a 2/1 format is recommended.

Alternatively, the "ranges" property may be empty, indicating that the
registers are visible on the parent bus using an identity mapping
translation.  In other words, the parent bus address space is the same
as the child bus address space.

2) Note about "compatible" properties
-------------------------------------

These properties are optional, but recommended in devices and the root
node. The format of a "compatible" property is a list of concatenated
zero terminated strings. They allow a device to express its
compatibility with a family of similar devices, in some cases,
allowing a single driver to match against several devices regardless
of their actual names.

3) Note about "name" properties
-------------------------------

While earlier users of Open Firmware like OldWorld macintoshes tended
to use the actual device name for the "name" property, it's nowadays
considered a good practice to use a name that is closer to the device
class (often equal to device_type). For example, nowadays, ethernet
controllers are named "ethernet", an additional "model" property
defining precisely the chip type/model, and "compatible" property
defining the family in case a single driver can driver more than one
of these chips. However, the kernel doesn't generally put any
restriction on the "name" property; it is simply considered good
practice to follow the standard and its evolutions as closely as
possible.

Note also that the new format version 16 makes the "name" property
optional. If it's absent for a node, then the node's unit name is then
used to reconstruct the name. That is, the part of the unit name
before the "@" sign is used (or the entire unit name if no "@" sign
is present).

4) Note about node and property names and character set
-------------------------------------------------------

While open firmware provides more flexible usage of 8859-1, this
specification enforces more strict rules. Nodes and properties should
be comprised only of ASCII characters 'a' to 'z', '0' to
'9', ',', '.', '_', '+', '#', '?', and '-'. Node names additionally
allow uppercase characters 'A' to 'Z' (property names should be
lowercase. The fact that vendors like Apple don't respect this rule is
irrelevant here). Additionally, node and property names should always
begin with a character in the range 'a' to 'z' (or 'A' to 'Z' for node
names).

The maximum number of characters for both nodes and property names
is 31. In the case of node names, this is only the leftmost part of
a unit name (the pure "name" property), it doesn't include the unit
address which can extend beyond that limit.


5) Required nodes and properties
--------------------------------
  These are all that are currently required. However, it is strongly
  recommended that you expose PCI host bridges as documented in the
  PCI binding to open firmware, and your interrupt tree as documented
  in OF interrupt tree specification.

  a) The root node

  The root node requires some properties to be present:

    - model : this is your board name/model
    - #address-cells : address representation for "root" devices
    - #size-cells: the size representation for "root" devices
    - device_type : This property shouldn't be necessary. However, if
      you decide to create a device_type for your root node, make sure it
      is _not_ "chrp" unless your platform is a pSeries or PAPR compliant
      one for 64-bit, or a CHRP-type machine for 32-bit as this will
      matched by the kernel this way.

  Additionally, some recommended properties are:

    - compatible : the board "family" generally finds its way here,
      for example, if you have 2 board models with a similar layout,
      that typically get driven by the same platform code in the
      kernel, you would use a different "model" property but put a
      value in "compatible". The kernel doesn't directly use that
      value but it is generally useful.

  The root node is also generally where you add additional properties
  specific to your board like the serial number if any, that sort of
  thing. It is recommended that if you add any "custom" property whose
  name may clash with standard defined ones, you prefix them with your
  vendor name and a comma.

  b) The /cpus node

  This node is the parent of all individual CPU nodes. It doesn't
  have any specific requirements, though it's generally good practice
  to have at least:

               #address-cells = <00000001>
               #size-cells    = <00000000>

  This defines that the "address" for a CPU is a single cell, and has
  no meaningful size. This is not necessary but the kernel will assume
  that format when reading the "reg" properties of a CPU node, see
  below

  c) The /cpus/* nodes

  So under /cpus, you are supposed to create a node for every CPU on
  the machine. There is no specific restriction on the name of the
  CPU, though It's common practice to call it PowerPC,<name>. For
  example, Apple uses PowerPC,G5 while IBM uses PowerPC,970FX.

  Required properties:

    - device_type : has to be "cpu"
    - reg : This is the physical CPU number, it's a single 32-bit cell
      and is also used as-is as the unit number for constructing the
      unit name in the full path. For example, with 2 CPUs, you would
      have the full path:
        /cpus/PowerPC,970FX@0
        /cpus/PowerPC,970FX@1
      (unit addresses do not require leading zeroes)
    - d-cache-block-size : one cell, L1 data cache block size in bytes (*)
    - i-cache-block-size : one cell, L1 instruction cache block size in
      bytes
    - d-cache-size : one cell, size of L1 data cache in bytes
    - i-cache-size : one cell, size of L1 instruction cache in bytes

(*) The cache "block" size is the size on which the cache management
instructions operate. Historically, this document used the cache
"line" size here which is incorrect. The kernel will prefer the cache
block size and will fallback to cache line size for backward
compatibility.

  Recommended properties:

    - timebase-frequency : a cell indicating the frequency of the
      timebase in Hz. This is not directly used by the generic code,
      but you are welcome to copy/paste the pSeries code for setting
      the kernel timebase/decrementer calibration based on this
      value.
    - clock-frequency : a cell indicating the CPU core clock frequency
      in Hz. A new property will be defined for 64-bit values, but if
      your frequency is < 4Ghz, one cell is enough. Here as well as
      for the above, the common code doesn't use that property, but
      you are welcome to re-use the pSeries or Maple one. A future
      kernel version might provide a common function for this.
    - d-cache-line-size : one cell, L1 data cache line size in bytes
      if different from the block size
    - i-cache-line-size : one cell, L1 instruction cache line size in
      bytes if different from the block size

  You are welcome to add any property you find relevant to your board,
  like some information about the mechanism used to soft-reset the
  CPUs. For example, Apple puts the GPIO number for CPU soft reset
  lines in there as a "soft-reset" property since they start secondary
  CPUs by soft-resetting them.


  d) the /memory node(s)

  To define the physical memory layout of your board, you should
  create one or more memory node(s). You can either create a single
  node with all memory ranges in its reg property, or you can create
  several nodes, as you wish. The unit address (@ part) used for the
  full path is the address of the first range of memory defined by a
  given node. If you use a single memory node, this will typically be
  @0.

  Required properties:

    - device_type : has to be "memory"
    - reg : This property contains all the physical memory ranges of
      your board. It's a list of addresses/sizes concatenated
      together, with the number of cells of each defined by the
      #address-cells and #size-cells of the root node. For example,
      with both of these properties being 2 like in the example given
      earlier, a 970 based machine with 6Gb of RAM could typically
      have a "reg" property here that looks like:

      00000000 00000000 00000000 80000000
      00000001 00000000 00000001 00000000

      That is a range starting at 0 of 0x80000000 bytes and a range
      starting at 0x100000000 and of 0x100000000 bytes. You can see
      that there is no memory covering the IO hole between 2Gb and
      4Gb. Some vendors prefer splitting those ranges into smaller
      segments, but the kernel doesn't care.

  e) The /chosen node

  This node is a bit "special". Normally, that's where open firmware
  puts some variable environment information, like the arguments, or
  the default input/output devices.

  This specification makes a few of these mandatory, but also defines
  some linux-specific properties that would be normally constructed by
  the prom_init() trampoline when booting with an OF client interface,
  but that you have to provide yourself when using the flattened format.

  Recommended properties:

    - bootargs : This zero-terminated string is passed as the kernel
      command line
    - linux,stdout-path : This is the full path to your standard
      console device if any. Typically, if you have serial devices on
      your board, you may want to put the full path to the one set as
      the default console in the firmware here, for the kernel to pick
      it up as its own default console. If you look at the function
      set_preferred_console() in arch/ppc64/kernel/setup.c, you'll see
      that the kernel tries to find out the default console and has
      knowledge of various types like 8250 serial ports. You may want
      to extend this function to add your own.

  Note that u-boot creates and fills in the chosen node for platforms
  that use it.

  (Note: a practice that is now obsolete was to include a property
  under /chosen called interrupt-controller which had a phandle value
  that pointed to the main interrupt controller)

  f) the /soc<SOCname> node

  This node is used to represent a system-on-a-chip (SOC) and must be
  present if the processor is a SOC. The top-level soc node contains
  information that is global to all devices on the SOC. The node name
  should contain a unit address for the SOC, which is the base address
  of the memory-mapped register set for the SOC. The name of an soc
  node should start with "soc", and the remainder of the name should
  represent the part number for the soc.  For example, the MPC8540's
  soc node would be called "soc8540".

  Required properties:

    - device_type : Should be "soc"
    - ranges : Should be defined as specified in 1) to describe the
      translation of SOC addresses for memory mapped SOC registers.
    - bus-frequency: Contains the bus frequency for the SOC node.
      Typically, the value of this field is filled in by the boot
      loader. 


  Recommended properties:

    - reg : This property defines the address and size of the
      memory-mapped registers that are used for the SOC node itself.
      It does not include the child device registers - these will be
      defined inside each child node.  The address specified in the
      "reg" property should match the unit address of the SOC node.
    - #address-cells : Address representation for "soc" devices.  The
      format of this field may vary depending on whether or not the
      device registers are memory mapped.  For memory mapped
      registers, this field represents the number of cells needed to
      represent the address of the registers.  For SOCs that do not
      use MMIO, a special address format should be defined that
      contains enough cells to represent the required information.
      See 1) above for more details on defining #address-cells.
    - #size-cells : Size representation for "soc" devices
    - #interrupt-cells : Defines the width of cells used to represent
       interrupts.  Typically this value is <2>, which includes a
       32-bit number that represents the interrupt number, and a
       32-bit number that represents the interrupt sense and level.
       This field is only needed if the SOC contains an interrupt
       controller.

  The SOC node may contain child nodes for each SOC device that the
  platform uses.  Nodes should not be created for devices which exist
  on the SOC but are not used by a particular platform. See chapter VI
  for more information on how to specify devices that are part of a SOC.

  Example SOC node for the MPC8540:

	soc8540@e0000000 {
		#address-cells = <1>;
		#size-cells = <1>;
		#interrupt-cells = <2>;
		device_type = "soc";
		ranges = <00000000 e0000000 00100000>
		reg = <e0000000 00003000>;
		bus-frequency = <0>;
	}



IV - "dtc", the device tree compiler
====================================


dtc source code can be found at
<http://ozlabs.org/~dgibson/dtc/dtc.tar.gz>

WARNING: This version is still in early development stage; the
resulting device-tree "blobs" have not yet been validated with the
kernel. The current generated bloc lacks a useful reserve map (it will
be fixed to generate an empty one, it's up to the bootloader to fill
it up) among others. The error handling needs work, bugs are lurking,
etc...

dtc basically takes a device-tree in a given format and outputs a
device-tree in another format. The currently supported formats are:

  Input formats:
  -------------

     - "dtb": "blob" format, that is a flattened device-tree block
       with
        header all in a binary blob.
     - "dts": "source" format. This is a text file containing a
       "source" for a device-tree. The format is defined later in this
        chapter.
     - "fs" format. This is a representation equivalent to the
        output of /proc/device-tree, that is nodes are directories and
	properties are files

 Output formats:
 ---------------

     - "dtb": "blob" format
     - "dts": "source" format
     - "asm": assembly language file. This is a file that can be
       sourced by gas to generate a device-tree "blob". That file can
       then simply be added to your Makefile. Additionally, the
       assembly file exports some symbols that can be used.


The syntax of the dtc tool is

    dtc [-I <input-format>] [-O <output-format>]
        [-o output-filename] [-V output_version] input_filename


The "output_version" defines what version of the "blob" format will be
generated. Supported versions are 1,2,3 and 16. The default is
currently version 3 but that may change in the future to version 16.

Additionally, dtc performs various sanity checks on the tree, like the
uniqueness of linux, phandle properties, validity of strings, etc...

The format of the .dts "source" file is "C" like, supports C and C++
style comments.

/ {
}

The above is the "device-tree" definition. It's the only statement
supported currently at the toplevel.

/ {
  property1 = "string_value";	/* define a property containing a 0
                                 * terminated string
				 */

  property2 = <1234abcd>;	/* define a property containing a
                                 * numerical 32-bit value (hexadecimal)
				 */

  property3 = <12345678 12345678 deadbeef>;
                                /* define a property containing 3
                                 * numerical 32-bit values (cells) in
                                 * hexadecimal
				 */
  property4 = [0a 0b 0c 0d de ea ad be ef];
                                /* define a property whose content is
                                 * an arbitrary array of bytes
                                 */

  childnode@addresss {	/* define a child node named "childnode"
                                 * whose unit name is "childnode at
				 * address"
                                 */

    childprop = "hello\n";      /* define a property "childprop" of
                                 * childnode (in this case, a string)
                                 */
  };
};

Nodes can contain other nodes etc... thus defining the hierarchical
structure of the tree.

Strings support common escape sequences from C: "\n", "\t", "\r",
"\(octal value)", "\x(hex value)".

It is also suggested that you pipe your source file through cpp (gcc
preprocessor) so you can use #include's, #define for constants, etc...

Finally, various options are planned but not yet implemented, like
automatic generation of phandles, labels (exported to the asm file so
you can point to a property content and change it easily from whatever
you link the device-tree with), label or path instead of numeric value
in some cells to "point" to a node (replaced by a phandle at compile
time), export of reserve map address to the asm file, ability to
specify reserve map content at compile time, etc...

We may provide a .h include file with common definitions of that
proves useful for some properties (like building PCI properties or
interrupt maps) though it may be better to add a notion of struct
definitions to the compiler...


V - Recommendations for a bootloader
====================================


Here are some various ideas/recommendations that have been proposed
while all this has been defined and implemented.

  - The bootloader may want to be able to use the device-tree itself
    and may want to manipulate it (to add/edit some properties,
    like physical memory size or kernel arguments). At this point, 2
    choices can be made. Either the bootloader works directly on the
    flattened format, or the bootloader has its own internal tree
    representation with pointers (similar to the kernel one) and
    re-flattens the tree when booting the kernel. The former is a bit
    more difficult to edit/modify, the later requires probably a bit
    more code to handle the tree structure. Note that the structure
    format has been designed so it's relatively easy to "insert"
    properties or nodes or delete them by just memmoving things
    around. It contains no internal offsets or pointers for this
    purpose.

  - An example of code for iterating nodes & retrieving properties
    directly from the flattened tree format can be found in the kernel
    file arch/ppc64/kernel/prom.c, look at scan_flat_dt() function,
    its usage in early_init_devtree(), and the corresponding various
    early_init_dt_scan_*() callbacks. That code can be re-used in a
    GPL bootloader, and as the author of that code, I would be happy
    to discuss possible free licensing to any vendor who wishes to
    integrate all or part of this code into a non-GPL bootloader.



VI - System-on-a-chip devices and nodes
=======================================

Many companies are now starting to develop system-on-a-chip
processors, where the processor core (CPU) and many peripheral devices
exist on a single piece of silicon.  For these SOCs, an SOC node
should be used that defines child nodes for the devices that make
up the SOC. While platforms are not required to use this model in
order to boot the kernel, it is highly encouraged that all SOC
implementations define as complete a flat-device-tree as possible to
describe the devices on the SOC.  This will allow for the
genericization of much of the kernel code.


1) Defining child nodes of an SOC
---------------------------------

Each device that is part of an SOC may have its own node entry inside
the SOC node.  For each device that is included in the SOC, the unit
address property represents the address offset for this device's
memory-mapped registers in the parent's address space.  The parent's
address space is defined by the "ranges" property in the top-level soc
node. The "reg" property for each node that exists directly under the
SOC node should contain the address mapping from the child address space
to the parent SOC address space and the size of the device's
memory-mapped register file.

For many devices that may exist inside an SOC, there are predefined
specifications for the format of the device tree node.  All SOC child
nodes should follow these specifications, except where noted in this
document.

See appendix A for an example partial SOC node definition for the
MPC8540.


2) Representing devices without a current OF specification
----------------------------------------------------------

Currently, there are many devices on SOCs that do not have a standard
representation pre-defined as part of the open firmware
specifications, mainly because the boards that contain these SOCs are
not currently booted using open firmware.   This section contains
descriptions for the SOC devices for which new nodes have been
defined; this list will expand as more and more SOC-containing
platforms are moved over to use the flattened-device-tree model.

  a) MDIO IO device

  The MDIO is a bus to which the PHY devices are connected.  For each
  device that exists on this bus, a child node should be created.  See
  the definition of the PHY node below for an example of how to define
  a PHY.

  Required properties:
    - reg : Offset and length of the register set for the device
    - compatible : Should define the compatible device type for the
      mdio.  Currently, this is most likely to be "fsl,gianfar-mdio"

  Example:

	mdio@24520 {
		reg = <24520 20>;
		compatible = "fsl,gianfar-mdio";

		ethernet-phy@0 {
			......
		};
	};


  b) Gianfar-compatible ethernet nodes

  Required properties:

    - device_type : Should be "network"
    - model : Model of the device.  Can be "TSEC", "eTSEC", or "FEC"
    - compatible : Should be "gianfar"
    - reg : Offset and length of the register set for the device
    - mac-address : List of bytes representing the ethernet address of
      this controller
    - interrupts : <a b> where a is the interrupt number and b is a
      field that represents an encoding of the sense and level
      information for the interrupt.  This should be encoded based on
      the information in section 2) depending on the type of interrupt
      controller you have.
    - interrupt-parent : the phandle for the interrupt controller that
      services interrupts for this device.
    - phy-handle : The phandle for the PHY connected to this ethernet
      controller.
    - fixed-link : <a b c d e> where a is emulated phy id - choose any,
      but unique to the all specified fixed-links, b is duplex - 0 half,
      1 full, c is link speed - d#10/d#100/d#1000, d is pause - 0 no
      pause, 1 pause, e is asym_pause - 0 no asym_pause, 1 asym_pause.

  Recommended properties:

    - linux,network-index : This is the intended "index" of this
      network device.  This is used by the bootwrapper to interpret
      MAC addresses passed by the firmware when no information other
      than indices is available to associate an address with a device.
    - phy-connection-type : a string naming the controller/PHY interface type,
      i.e., "mii" (default), "rmii", "gmii", "rgmii", "rgmii-id", "sgmii",
      "tbi", or "rtbi".  This property is only really needed if the connection
      is of type "rgmii-id", as all other connection types are detected by
      hardware.


  Example:

	ethernet@24000 {
		#size-cells = <0>;
		device_type = "network";
		model = "TSEC";
		compatible = "gianfar";
		reg = <24000 1000>;
		mac-address = [ 00 E0 0C 00 73 00 ];
		interrupts = <d 3 e 3 12 3>;
		interrupt-parent = <40000>;
		phy-handle = <2452000>
	};



   c) PHY nodes

   Required properties:

    - device_type : Should be "ethernet-phy"
    - interrupts : <a b> where a is the interrupt number and b is a
      field that represents an encoding of the sense and level
      information for the interrupt.  This should be encoded based on
      the information in section 2) depending on the type of interrupt
      controller you have.
    - interrupt-parent : the phandle for the interrupt controller that
      services interrupts for this device.
    - reg : The ID number for the phy, usually a small integer
    - linux,phandle :  phandle for this node; likely referenced by an
      ethernet controller node.


   Example:

	ethernet-phy@0 {
		linux,phandle = <2452000>
		interrupt-parent = <40000>;
		interrupts = <35 1>;
		reg = <0>;
		device_type = "ethernet-phy";
	};


   d) Interrupt controllers

   Some SOC devices contain interrupt controllers that are different
   from the standard Open PIC specification.  The SOC device nodes for
   these types of controllers should be specified just like a standard
   OpenPIC controller.  Sense and level information should be encoded
   as specified in section 2) of this chapter for each device that
   specifies an interrupt.

   Example :

	pic@40000 {
		linux,phandle = <40000>;
		clock-frequency = <0>;
		interrupt-controller;
		#address-cells = <0>;
		reg = <40000 40000>;
		built-in;
		compatible = "chrp,open-pic";
		device_type = "open-pic";
		big-endian;
	};


   e) I2C

   Required properties :

    - device_type : Should be "i2c"
    - reg : Offset and length of the register set for the device

   Recommended properties :

    - compatible : Should be "fsl-i2c" for parts compatible with
      Freescale I2C specifications.
    - interrupts : <a b> where a is the interrupt number and b is a
      field that represents an encoding of the sense and level
      information for the interrupt.  This should be encoded based on
      the information in section 2) depending on the type of interrupt
      controller you have.
    - interrupt-parent : the phandle for the interrupt controller that
      services interrupts for this device.
    - dfsrr : boolean; if defined, indicates that this I2C device has
      a digital filter sampling rate register
    - fsl5200-clocking : boolean; if defined, indicated that this device
      uses the FSL 5200 clocking mechanism.

   Example :

	i2c@3000 {
		interrupt-parent = <40000>;
		interrupts = <1b 3>;
		reg = <3000 18>;
		device_type = "i2c";
		compatible  = "fsl-i2c";
		dfsrr;
	};


   f) Freescale SOC USB controllers

   The device node for a USB controller that is part of a Freescale
   SOC is as described in the document "Open Firmware Recommended
   Practice : Universal Serial Bus" with the following modifications
   and additions :  

   Required properties :
    - compatible : Should be "fsl-usb2-mph" for multi port host USB
      controllers, or "fsl-usb2-dr" for dual role USB controllers
    - phy_type : For multi port host USB controllers, should be one of
      "ulpi", or "serial". For dual role USB controllers, should be
      one of "ulpi", "utmi", "utmi_wide", or "serial".
    - reg : Offset and length of the register set for the device
    - port0 : boolean; if defined, indicates port0 is connected for
      fsl-usb2-mph compatible controllers.  Either this property or
      "port1" (or both) must be defined for "fsl-usb2-mph" compatible 
      controllers.
    - port1 : boolean; if defined, indicates port1 is connected for
      fsl-usb2-mph compatible controllers.  Either this property or
      "port0" (or both) must be defined for "fsl-usb2-mph" compatible 
      controllers.
    - dr_mode : indicates the working mode for "fsl-usb2-dr" compatible
      controllers.  Can be "host", "peripheral", or "otg".  Default to
      "host" if not defined for backward compatibility.

   Recommended properties :
    - interrupts : <a b> where a is the interrupt number and b is a
      field that represents an encoding of the sense and level
      information for the interrupt.  This should be encoded based on
      the information in section 2) depending on the type of interrupt
      controller you have.
    - interrupt-parent : the phandle for the interrupt controller that
      services interrupts for this device.

   Example multi port host USB controller device node :
	usb@22000 {
		compatible = "fsl-usb2-mph";
		reg = <22000 1000>;
		#address-cells = <1>;
		#size-cells = <0>;
		interrupt-parent = <700>;
		interrupts = <27 1>;
		phy_type = "ulpi";
		port0;
		port1;
	};

   Example dual role USB controller device node :
	usb@23000 {
		compatible = "fsl-usb2-dr";
		reg = <23000 1000>;
		#address-cells = <1>;
		#size-cells = <0>;
		interrupt-parent = <700>;
		interrupts = <26 1>;
		dr_mode = "otg";
		phy = "ulpi";
	};


   g) Freescale SOC SEC Security Engines

   Required properties:

    - device_type : Should be "crypto"
    - model : Model of the device.  Should be "SEC1" or "SEC2"
    - compatible : Should be "talitos"
    - reg : Offset and length of the register set for the device
    - interrupts : <a b> where a is the interrupt number and b is a
      field that represents an encoding of the sense and level
      information for the interrupt.  This should be encoded based on
      the information in section 2) depending on the type of interrupt
      controller you have.
    - interrupt-parent : the phandle for the interrupt controller that
      services interrupts for this device.
    - num-channels : An integer representing the number of channels
      available.
    - channel-fifo-len : An integer representing the number of
      descriptor pointers each channel fetch fifo can hold.
    - exec-units-mask : The bitmask representing what execution units
      (EUs) are available. It's a single 32-bit cell. EU information
      should be encoded following the SEC's Descriptor Header Dword
      EU_SEL0 field documentation, i.e. as follows:

        bit 0 = reserved - should be 0
        bit 1 = set if SEC has the ARC4 EU (AFEU)
        bit 2 = set if SEC has the DES/3DES EU (DEU)
        bit 3 = set if SEC has the message digest EU (MDEU)
        bit 4 = set if SEC has the random number generator EU (RNG)
        bit 5 = set if SEC has the public key EU (PKEU)
        bit 6 = set if SEC has the AES EU (AESU)
        bit 7 = set if SEC has the Kasumi EU (KEU)

      bits 8 through 31 are reserved for future SEC EUs.

    - descriptor-types-mask : The bitmask representing what descriptors
      are available. It's a single 32-bit cell. Descriptor type
      information should be encoded following the SEC's Descriptor
      Header Dword DESC_TYPE field documentation, i.e. as follows:

        bit 0  = set if SEC supports the aesu_ctr_nonsnoop desc. type
        bit 1  = set if SEC supports the ipsec_esp descriptor type
        bit 2  = set if SEC supports the common_nonsnoop desc. type
        bit 3  = set if SEC supports the 802.11i AES ccmp desc. type
        bit 4  = set if SEC supports the hmac_snoop_no_afeu desc. type
        bit 5  = set if SEC supports the srtp descriptor type
        bit 6  = set if SEC supports the non_hmac_snoop_no_afeu desc.type
        bit 7  = set if SEC supports the pkeu_assemble descriptor type
        bit 8  = set if SEC supports the aesu_key_expand_output desc.type
        bit 9  = set if SEC supports the pkeu_ptmul descriptor type
        bit 10 = set if SEC supports the common_nonsnoop_afeu desc. type
        bit 11 = set if SEC supports the pkeu_ptadd_dbl descriptor type

      ..and so on and so forth.

   Example:

       /* MPC8548E */
       crypto@30000 {
               device_type = "crypto";
               model = "SEC2";
               compatible = "talitos";
               reg = <30000 10000>;
               interrupts = <1d 3>;
               interrupt-parent = <40000>;
               num-channels = <4>;
               channel-fifo-len = <18>;
               exec-units-mask = <000000fe>;
               descriptor-types-mask = <012b0ebf>;
       };

   h) Board Control and Status (BCSR)

   Required properties:

    - device_type : Should be "board-control"
    - reg : Offset and length of the register set for the device

    Example:

	bcsr@f8000000 {
		device_type = "board-control";
		reg = <f8000000 8000>;
	};

   i) Freescale QUICC Engine module (QE)
   This represents qe module that is installed on PowerQUICC II Pro.

   NOTE:  This is an interim binding; it should be updated to fit
   in with the CPM binding later in this document.

   Basically, it is a bus of devices, that could act more or less
   as a complete entity (UCC, USB etc ). All of them should be siblings on
   the "root" qe node, using the common properties from there.
   The description below applies to the qe of MPC8360 and
   more nodes and properties would be extended in the future.

   i) Root QE device

   Required properties:
   - compatible : should be "fsl,qe";
   - model : precise model of the QE, Can be "QE", "CPM", or "CPM2"
   - reg : offset and length of the device registers.
   - bus-frequency : the clock frequency for QUICC Engine.

   Recommended properties
   - brg-frequency : the internal clock source frequency for baud-rate
     generators in Hz.

   Example:
	qe@e0100000 {
		#address-cells = <1>;
		#size-cells = <1>;
		#interrupt-cells = <2>;
		compatible = "fsl,qe";
		ranges = <0 e0100000 00100000>;
		reg = <e0100000 480>;
		brg-frequency = <0>;
		bus-frequency = <179A7B00>;
	}


   ii) SPI (Serial Peripheral Interface)

   Required properties:
   - cell-index : SPI controller index.
   - compatible : should be "fsl,spi".
   - mode : the SPI operation mode, it can be "cpu" or "cpu-qe".
   - reg : Offset and length of the register set for the device
   - interrupts : <a b> where a is the interrupt number and b is a
     field that represents an encoding of the sense and level
     information for the interrupt.  This should be encoded based on
     the information in section 2) depending on the type of interrupt
     controller you have.
   - interrupt-parent : the phandle for the interrupt controller that
     services interrupts for this device.

   Example:
	spi@4c0 {
		cell-index = <0>;
		compatible = "fsl,spi";
		reg = <4c0 40>;
		interrupts = <82 0>;
		interrupt-parent = <700>;
		mode = "cpu";
	};


   iii) USB (Universal Serial Bus Controller)

   Required properties:
   - compatible : could be "qe_udc" or "fhci-hcd".
   - mode : the could be "host" or "slave".
   - reg : Offset and length of the register set for the device
   - interrupts : <a b> where a is the interrupt number and b is a
     field that represents an encoding of the sense and level
     information for the interrupt.  This should be encoded based on
     the information in section 2) depending on the type of interrupt
     controller you have.
   - interrupt-parent : the phandle for the interrupt controller that
     services interrupts for this device.

   Example(slave):
	usb@6c0 {
		compatible = "qe_udc";
		reg = <6c0 40>;
		interrupts = <8b 0>;
		interrupt-parent = <700>;
		mode = "slave";
	};


   iv) UCC (Unified Communications Controllers)

   Required properties:
   - device_type : should be "network", "hldc", "uart", "transparent"
     "bisync", "atm", or "serial".
   - compatible : could be "ucc_geth" or "fsl_atm" and so on.
   - model : should be "UCC".
   - device-id : the ucc number(1-8), corresponding to UCCx in UM.
   - reg : Offset and length of the register set for the device
   - interrupts : <a b> where a is the interrupt number and b is a
     field that represents an encoding of the sense and level
     information for the interrupt.  This should be encoded based on
     the information in section 2) depending on the type of interrupt
     controller you have.
   - interrupt-parent : the phandle for the interrupt controller that
     services interrupts for this device.
   - pio-handle : The phandle for the Parallel I/O port configuration.
   - port-number : for UART drivers, the port number to use, between 0 and 3.
     This usually corresponds to the /dev/ttyQE device, e.g. <0> = /dev/ttyQE0.
     The port number is added to the minor number of the device.  Unlike the
     CPM UART driver, the port-number is required for the QE UART driver.
   - soft-uart : for UART drivers, if specified this means the QE UART device
     driver should use "Soft-UART" mode, which is needed on some SOCs that have
     broken UART hardware.  Soft-UART is provided via a microcode upload.
   - rx-clock-name: the UCC receive clock source
     "none": clock source is disabled
     "brg1" through "brg16": clock source is BRG1-BRG16, respectively
     "clk1" through "clk24": clock source is CLK1-CLK24, respectively
   - tx-clock-name: the UCC transmit clock source
     "none": clock source is disabled
     "brg1" through "brg16": clock source is BRG1-BRG16, respectively
     "clk1" through "clk24": clock source is CLK1-CLK24, respectively
   The following two properties are deprecated.  rx-clock has been replaced
   with rx-clock-name, and tx-clock has been replaced with tx-clock-name.
   Drivers that currently use the deprecated properties should continue to
   do so, in order to support older device trees, but they should be updated
   to check for the new properties first.
   - rx-clock : represents the UCC receive clock source.
     0x00 : clock source is disabled;
     0x1~0x10 : clock source is BRG1~BRG16 respectively;
     0x11~0x28: clock source is QE_CLK1~QE_CLK24 respectively.
   - tx-clock: represents the UCC transmit clock source;
     0x00 : clock source is disabled;
     0x1~0x10 : clock source is BRG1~BRG16 respectively;
     0x11~0x28: clock source is QE_CLK1~QE_CLK24 respectively.

   Required properties for network device_type:
   - mac-address : list of bytes representing the ethernet address.
   - phy-handle : The phandle for the PHY connected to this controller.

   Recommended properties:
   - linux,network-index : This is the intended "index" of this
     network device.  This is used by the bootwrapper to interpret
     MAC addresses passed by the firmware when no information other
     than indices is available to associate an address with a device.
   - phy-connection-type : a string naming the controller/PHY interface type,
     i.e., "mii" (default), "rmii", "gmii", "rgmii", "rgmii-id" (Internal
     Delay), "rgmii-txid" (delay on TX only), "rgmii-rxid" (delay on RX only),
     "tbi", or "rtbi".

   Example:
	ucc@2000 {
		device_type = "network";
		compatible = "ucc_geth";
		model = "UCC";
		device-id = <1>;
		reg = <2000 200>;
		interrupts = <a0 0>;
		interrupt-parent = <700>;
		mac-address = [ 00 04 9f 00 23 23 ];
		rx-clock = "none";
		tx-clock = "clk9";
		phy-handle = <212000>;
		phy-connection-type = "gmii";
		pio-handle = <140001>;
	};


   v) Parallel I/O Ports

   This node configures Parallel I/O ports for CPUs with QE support.
   The node should reside in the "soc" node of the tree.  For each
   device that using parallel I/O ports, a child node should be created.
   See the definition of the Pin configuration nodes below for more
   information.

   Required properties:
   - device_type : should be "par_io".
   - reg : offset to the register set and its length.
   - num-ports : number of Parallel I/O ports

   Example:
	par_io@1400 {
		reg = <1400 100>;
		#address-cells = <1>;
		#size-cells = <0>;
		device_type = "par_io";
		num-ports = <7>;
		ucc_pin@01 {
			......
		};


   vi) Pin configuration nodes

   Required properties:
   - linux,phandle : phandle of this node; likely referenced by a QE
     device.
   - pio-map : array of pin configurations.  Each pin is defined by 6
     integers.  The six numbers are respectively: port, pin, dir,
     open_drain, assignment, has_irq.
     - port : port number of the pin; 0-6 represent port A-G in UM.
     - pin : pin number in the port.
     - dir : direction of the pin, should encode as follows:

	0 = The pin is disabled
	1 = The pin is an output
	2 = The pin is an input
	3 = The pin is I/O

     - open_drain : indicates the pin is normal or wired-OR:

	0 = The pin is actively driven as an output
	1 = The pin is an open-drain driver. As an output, the pin is
	    driven active-low, otherwise it is three-stated.

     - assignment : function number of the pin according to the Pin Assignment
       tables in User Manual.  Each pin can have up to 4 possible functions in
       QE and two options for CPM.
     - has_irq : indicates if the pin is used as source of external
       interrupts.

   Example:
	ucc_pin@01 {
		linux,phandle = <140001>;
		pio-map = <
		/* port  pin  dir  open_drain  assignment  has_irq */
			0  3  1  0  1  0 	/* TxD0 */
			0  4  1  0  1  0 	/* TxD1 */
			0  5  1  0  1  0 	/* TxD2 */
			0  6  1  0  1  0 	/* TxD3 */
			1  6  1  0  3  0 	/* TxD4 */
			1  7  1  0  1  0 	/* TxD5 */
			1  9  1  0  2  0 	/* TxD6 */
			1  a  1  0  2  0 	/* TxD7 */
			0  9  2  0  1  0 	/* RxD0 */
			0  a  2  0  1  0 	/* RxD1 */
			0  b  2  0  1  0 	/* RxD2 */
			0  c  2  0  1  0 	/* RxD3 */
			0  d  2  0  1  0 	/* RxD4 */
			1  1  2  0  2  0 	/* RxD5 */
			1  0  2  0  2  0 	/* RxD6 */
			1  4  2  0  2  0 	/* RxD7 */
			0  7  1  0  1  0 	/* TX_EN */
			0  8  1  0  1  0 	/* TX_ER */
			0  f  2  0  1  0 	/* RX_DV */
			0  10 2  0  1  0 	/* RX_ER */
			0  0  2  0  1  0 	/* RX_CLK */
			2  9  1  0  3  0 	/* GTX_CLK - CLK10 */
			2  8  2  0  1  0>;	/* GTX125 - CLK9 */
	};

   vii) Multi-User RAM (MURAM)

   Required properties:
   - compatible : should be "fsl,qe-muram", "fsl,cpm-muram".
   - mode : the could be "host" or "slave".
   - ranges : Should be defined as specified in 1) to describe the
      translation of MURAM addresses.
   - data-only : sub-node which defines the address area under MURAM
      bus that can be allocated as data/parameter

   Example:

	muram@10000 {
		compatible = "fsl,qe-muram", "fsl,cpm-muram";
		ranges = <0 00010000 0000c000>;

		data-only@0{
			compatible = "fsl,qe-muram-data",
				     "fsl,cpm-muram-data";
			reg = <0 c000>;
		};
	};

   viii) Uploaded QE firmware

	 If a new firwmare has been uploaded to the QE (usually by the
	 boot loader), then a 'firmware' child node should be added to the QE
	 node.  This node provides information on the uploaded firmware that
	 device drivers may need.

	 Required properties:
	 - id: The string name of the firmware.  This is taken from the 'id'
	       member of the qe_firmware structure of the uploaded firmware.
	       Device drivers can search this string to determine if the
	       firmware they want is already present.
	 - extended-modes: The Extended Modes bitfield, taken from the
			   firmware binary.  It is a 64-bit number represented
			   as an array of two 32-bit numbers.
	 - virtual-traps: The virtual traps, taken from the firmware binary.
			  It is an array of 8 32-bit numbers.

	 Example:

		firmware {
			id = "Soft-UART";
			extended-modes = <0 0>;
			virtual-traps = <0 0 0 0 0 0 0 0>;
		}

   j) CFI or JEDEC memory-mapped NOR flash

    Flash chips (Memory Technology Devices) are often used for solid state
    file systems on embedded devices.

     - compatible : should contain the specific model of flash chip(s)
       used, if known, followed by either "cfi-flash" or "jedec-flash"
     - reg : Address range of the flash chip
     - bank-width : Width (in bytes) of the flash bank.  Equal to the
       device width times the number of interleaved chips.
     - device-width : (optional) Width of a single flash chip.  If
       omitted, assumed to be equal to 'bank-width'.
     - #address-cells, #size-cells : Must be present if the flash has
       sub-nodes representing partitions (see below).  In this case
       both #address-cells and #size-cells must be equal to 1.

    For JEDEC compatible devices, the following additional properties
    are defined:

     - vendor-id : Contains the flash chip's vendor id (1 byte).
     - device-id : Contains the flash chip's device id (1 byte).

    In addition to the information on the flash bank itself, the
    device tree may optionally contain additional information
    describing partitions of the flash address space.  This can be
    used on platforms which have strong conventions about which
    portions of the flash are used for what purposes, but which don't
    use an on-flash partition table such as RedBoot.

    Each partition is represented as a sub-node of the flash device.
    Each node's name represents the name of the corresponding
    partition of the flash device.

    Flash partitions
     - reg : The partition's offset and size within the flash bank.
     - label : (optional) The label / name for this flash partition.
       If omitted, the label is taken from the node name (excluding
       the unit address).
     - read-only : (optional) This parameter, if present, is a hint to
       Linux that this flash partition should only be mounted
       read-only.  This is usually used for flash partitions
       containing early-boot firmware images or data which should not
       be clobbered.

    Example:

	flash@ff000000 {
		compatible = "amd,am29lv128ml", "cfi-flash";
		reg = <ff000000 01000000>;
		bank-width = <4>;
		device-width = <1>;
		#address-cells = <1>;
		#size-cells = <1>;
		fs@0 {
			label = "fs";
			reg = <0 f80000>;
		};
		firmware@f80000 {
			label ="firmware";
			reg = <f80000 80000>;
			read-only;
		};
	};

   k) Global Utilities Block

   The global utilities block controls power management, I/O device
   enabling, power-on-reset configuration monitoring, general-purpose
   I/O signal configuration, alternate function selection for multiplexed
   signals, and clock control.

   Required properties:

    - compatible : Should define the compatible device type for
      global-utilities.
    - reg : Offset and length of the register set for the device.

  Recommended properties:

    - fsl,has-rstcr : Indicates that the global utilities register set
      contains a functioning "reset control register" (i.e. the board
      is wired to reset upon setting the HRESET_REQ bit in this register).

    Example:

	global-utilities@e0000 {	/* global utilities block */
		compatible = "fsl,mpc8548-guts";
		reg = <e0000 1000>;
		fsl,has-rstcr;
	};

   l) Freescale Communications Processor Module

   NOTE: This is an interim binding, and will likely change slightly,
   as more devices are supported.  The QE bindings especially are
   incomplete.

   i) Root CPM node

   Properties:
   - compatible : "fsl,cpm1", "fsl,cpm2", or "fsl,qe".
   - reg : A 48-byte region beginning with CPCR.

   Example:
	cpm@119c0 {
		#address-cells = <1>;
		#size-cells = <1>;
		#interrupt-cells = <2>;
		compatible = "fsl,mpc8272-cpm", "fsl,cpm2";
		reg = <119c0 30>;
	}

   ii) Properties common to mulitple CPM/QE devices

   - fsl,cpm-command : This value is ORed with the opcode and command flag
                       to specify the device on which a CPM command operates.

   - fsl,cpm-brg : Indicates which baud rate generator the device
                   is associated with.  If absent, an unused BRG
                   should be dynamically allocated.  If zero, the
                   device uses an external clock rather than a BRG.

   - reg : Unless otherwise specified, the first resource represents the
           scc/fcc/ucc registers, and the second represents the device's
           parameter RAM region (if it has one).

   iii) Serial

   Currently defined compatibles:
   - fsl,cpm1-smc-uart
   - fsl,cpm2-smc-uart
   - fsl,cpm1-scc-uart
   - fsl,cpm2-scc-uart
   - fsl,qe-uart

   Example:

	serial@11a00 {
		device_type = "serial";
		compatible = "fsl,mpc8272-scc-uart",
		             "fsl,cpm2-scc-uart";
		reg = <11a00 20 8000 100>;
		interrupts = <28 8>;
		interrupt-parent = <&PIC>;
		fsl,cpm-brg = <1>;
		fsl,cpm-command = <00800000>;
	};

   iii) Network

   Currently defined compatibles:
   - fsl,cpm1-scc-enet
   - fsl,cpm2-scc-enet
   - fsl,cpm1-fec-enet
   - fsl,cpm2-fcc-enet (third resource is GFEMR)
   - fsl,qe-enet

   Example:

	ethernet@11300 {
		device_type = "network";
		compatible = "fsl,mpc8272-fcc-enet",
		             "fsl,cpm2-fcc-enet";
		reg = <11300 20 8400 100 11390 1>;
		local-mac-address = [ 00 00 00 00 00 00 ];
		interrupts = <20 8>;
		interrupt-parent = <&PIC>;
		phy-handle = <&PHY0>;
		linux,network-index = <0>;
		fsl,cpm-command = <12000300>;
	};

   iv) MDIO

   Currently defined compatibles:
   fsl,pq1-fec-mdio (reg is same as first resource of FEC device)
   fsl,cpm2-mdio-bitbang (reg is port C registers)

   Properties for fsl,cpm2-mdio-bitbang:
   fsl,mdio-pin : pin of port C controlling mdio data
   fsl,mdc-pin : pin of port C controlling mdio clock

   Example:

	mdio@10d40 {
		device_type = "mdio";
		compatible = "fsl,mpc8272ads-mdio-bitbang",
		             "fsl,mpc8272-mdio-bitbang",
		             "fsl,cpm2-mdio-bitbang";
		reg = <10d40 14>;
		#address-cells = <1>;
		#size-cells = <0>;
		fsl,mdio-pin = <12>;
		fsl,mdc-pin = <13>;
	};

   v) Baud Rate Generators

   Currently defined compatibles:
   fsl,cpm-brg
   fsl,cpm1-brg
   fsl,cpm2-brg

   Properties:
   - reg : There may be an arbitrary number of reg resources; BRG
     numbers are assigned to these in order.
   - clock-frequency : Specifies the base frequency driving
     the BRG.

   Example:

	brg@119f0 {
		compatible = "fsl,mpc8272-brg",
		             "fsl,cpm2-brg",
		             "fsl,cpm-brg";
		reg = <119f0 10 115f0 10>;
		clock-frequency = <d#25000000>;
	};

   vi) Interrupt Controllers

   Currently defined compatibles:
   - fsl,cpm1-pic
     - only one interrupt cell
   - fsl,pq1-pic
   - fsl,cpm2-pic
     - second interrupt cell is level/sense:
       - 2 is falling edge
       - 8 is active low

   Example:

	interrupt-controller@10c00 {
		#interrupt-cells = <2>;
		interrupt-controller;
		reg = <10c00 80>;
		compatible = "mpc8272-pic", "fsl,cpm2-pic";
	};

   vii) USB (Universal Serial Bus Controller)

   Properties:
   - compatible : "fsl,cpm1-usb", "fsl,cpm2-usb", "fsl,qe-usb"

   Example:
	usb@11bc0 {
		#address-cells = <1>;
		#size-cells = <0>;
		compatible = "fsl,cpm2-usb";
		reg = <11b60 18 8b00 100>;
		interrupts = <b 8>;
		interrupt-parent = <&PIC>;
		fsl,cpm-command = <2e600000>;
	};

   viii) Multi-User RAM (MURAM)

   The multi-user/dual-ported RAM is expressed as a bus under the CPM node.

   Ranges must be set up subject to the following restrictions:

   - Children's reg nodes must be offsets from the start of all muram, even
     if the user-data area does not begin at zero.
   - If multiple range entries are used, the difference between the parent
     address and the child address must be the same in all, so that a single
     mapping can cover them all while maintaining the ability to determine
     CPM-side offsets with pointer subtraction.  It is recommended that
     multiple range entries not be used.
   - A child address of zero must be translatable, even if no reg resources
     contain it.

   A child "data" node must exist, compatible with "fsl,cpm-muram-data", to
   indicate the portion of muram that is usable by the OS for arbitrary
   purposes.  The data node may have an arbitrary number of reg resources,
   all of which contribute to the allocatable muram pool.

   Example, based on mpc8272:

	muram@0 {
		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0 0 10000>;

		data@0 {
			compatible = "fsl,cpm-muram-data";
			reg = <0 2000 9800 800>;
		};
	};

   m) Chipselect/Local Bus

   Properties:
   - name : Should be localbus
   - #address-cells : Should be either two or three.  The first cell is the
                      chipselect number, and the remaining cells are the
                      offset into the chipselect.
   - #size-cells : Either one or two, depending on how large each chipselect
                   can be.
   - ranges : Each range corresponds to a single chipselect, and cover
              the entire access window as configured.

   Example:
	localbus@f0010100 {
		compatible = "fsl,mpc8272-localbus",
		             "fsl,pq2-localbus";
		#address-cells = <2>;
		#size-cells = <1>;
		reg = <f0010100 40>;

		ranges = <0 0 fe000000 02000000
		          1 0 f4500000 00008000>;

		flash@0,0 {
			compatible = "jedec-flash";
			reg = <0 0 2000000>;
			bank-width = <4>;
			device-width = <1>;
		};

		board-control@1,0 {
			reg = <1 0 20>;
			compatible = "fsl,mpc8272ads-bcsr";
		};
	};


    n) 4xx/Axon EMAC ethernet nodes

    The EMAC ethernet controller in IBM and AMCC 4xx chips, and also
    the Axon bridge.  To operate this needs to interact with a ths
    special McMAL DMA controller, and sometimes an RGMII or ZMII
    interface.  In addition to the nodes and properties described
    below, the node for the OPB bus on which the EMAC sits must have a
    correct clock-frequency property.

      i) The EMAC node itself

    Required properties:
    - device_type       : "network"

    - compatible        : compatible list, contains 2 entries, first is
			  "ibm,emac-CHIP" where CHIP is the host ASIC (440gx,
			  405gp, Axon) and second is either "ibm,emac" or
			  "ibm,emac4".  For Axon, thus, we have: "ibm,emac-axon",
			  "ibm,emac4"
    - interrupts        : <interrupt mapping for EMAC IRQ and WOL IRQ>
    - interrupt-parent  : optional, if needed for interrupt mapping
    - reg               : <registers mapping>
    - local-mac-address : 6 bytes, MAC address
    - mal-device        : phandle of the associated McMAL node
    - mal-tx-channel    : 1 cell, index of the tx channel on McMAL associated
			  with this EMAC
    - mal-rx-channel    : 1 cell, index of the rx channel on McMAL associated
			  with this EMAC
    - cell-index        : 1 cell, hardware index of the EMAC cell on a given
			  ASIC (typically 0x0 and 0x1 for EMAC0 and EMAC1 on
			  each Axon chip)
    - max-frame-size    : 1 cell, maximum frame size supported in bytes
    - rx-fifo-size      : 1 cell, Rx fifo size in bytes for 10 and 100 Mb/sec
			  operations.
			  For Axon, 2048
    - tx-fifo-size      : 1 cell, Tx fifo size in bytes for 10 and 100 Mb/sec
			  operations.
			  For Axon, 2048.
    - fifo-entry-size   : 1 cell, size of a fifo entry (used to calculate
			  thresholds).
			  For Axon, 0x00000010
    - mal-burst-size    : 1 cell, MAL burst size (used to calculate thresholds)
			  in bytes.
			  For Axon, 0x00000100 (I think ...)
    - phy-mode          : string, mode of operations of the PHY interface.
			  Supported values are: "mii", "rmii", "smii", "rgmii",
			  "tbi", "gmii", rtbi", "sgmii".
			  For Axon on CAB, it is "rgmii"
    - mdio-device       : 1 cell, required iff using shared MDIO registers
			  (440EP).  phandle of the EMAC to use to drive the
			  MDIO lines for the PHY used by this EMAC.
    - zmii-device       : 1 cell, required iff connected to a ZMII.  phandle of
			  the ZMII device node
    - zmii-channel      : 1 cell, required iff connected to a ZMII.  Which ZMII
			  channel or 0xffffffff if ZMII is only used for MDIO.
    - rgmii-device      : 1 cell, required iff connected to an RGMII. phandle
			  of the RGMII device node.
			  For Axon: phandle of plb5/plb4/opb/rgmii
    - rgmii-channel     : 1 cell, required iff connected to an RGMII.  Which
			  RGMII channel is used by this EMAC.
			  Fox Axon: present, whatever value is appropriate for each
			  EMAC, that is the content of the current (bogus) "phy-port"
			  property.

    Recommended properties:
    - linux,network-index : This is the intended "index" of this
      network device.  This is used by the bootwrapper to interpret
      MAC addresses passed by the firmware when no information other
      than indices is available to associate an address with a device.

    Optional properties:
    - phy-address       : 1 cell, optional, MDIO address of the PHY. If absent,
			  a search is performed.
    - phy-map           : 1 cell, optional, bitmap of addresses to probe the PHY
			  for, used if phy-address is absent. bit 0x00000001 is
			  MDIO address 0.
			  For Axon it can be absent, thouugh my current driver
			  doesn't handle phy-address yet so for now, keep
			  0x00ffffff in it.
    - rx-fifo-size-gige : 1 cell, Rx fifo size in bytes for 1000 Mb/sec
			  operations (if absent the value is the same as
			  rx-fifo-size).  For Axon, either absent or 2048.
    - tx-fifo-size-gige : 1 cell, Tx fifo size in bytes for 1000 Mb/sec
			  operations (if absent the value is the same as
			  tx-fifo-size). For Axon, either absent or 2048.
    - tah-device        : 1 cell, optional. If connected to a TAH engine for
			  offload, phandle of the TAH device node.
    - tah-channel       : 1 cell, optional. If appropriate, channel used on the
			  TAH engine.

    Example:

	EMAC0: ethernet@40000800 {
		linux,network-index = <0>;
		device_type = "network";
		compatible = "ibm,emac-440gp", "ibm,emac";
		interrupt-parent = <&UIC1>;
		interrupts = <1c 4 1d 4>;
		reg = <40000800 70>;
		local-mac-address = [00 04 AC E3 1B 1E];
		mal-device = <&MAL0>;
		mal-tx-channel = <0 1>;
		mal-rx-channel = <0>;
		cell-index = <0>;
		max-frame-size = <5dc>;
		rx-fifo-size = <1000>;
		tx-fifo-size = <800>;
		phy-mode = "rmii";
		phy-map = <00000001>;
		zmii-device = <&ZMII0>;
		zmii-channel = <0>;
	};

      ii) McMAL node

    Required properties:
    - device_type        : "dma-controller"
    - compatible         : compatible list, containing 2 entries, first is
			   "ibm,mcmal-CHIP" where CHIP is the host ASIC (like
			   emac) and the second is either "ibm,mcmal" or
			   "ibm,mcmal2".
			   For Axon, "ibm,mcmal-axon","ibm,mcmal2"
    - interrupts         : <interrupt mapping for the MAL interrupts sources:
                           5 sources: tx_eob, rx_eob, serr, txde, rxde>.
                           For Axon: This is _different_ from the current
			   firmware.  We use the "delayed" interrupts for txeob
			   and rxeob. Thus we end up with mapping those 5 MPIC
			   interrupts, all level positive sensitive: 10, 11, 32,
			   33, 34 (in decimal)
    - dcr-reg            : < DCR registers range >
    - dcr-parent         : if needed for dcr-reg
    - num-tx-chans       : 1 cell, number of Tx channels
    - num-rx-chans       : 1 cell, number of Rx channels

      iii) ZMII node

    Required properties:
    - compatible         : compatible list, containing 2 entries, first is
			   "ibm,zmii-CHIP" where CHIP is the host ASIC (like
			   EMAC) and the second is "ibm,zmii".
			   For Axon, there is no ZMII node.
    - reg                : <registers mapping>

      iv) RGMII node

    Required properties:
    - compatible         : compatible list, containing 2 entries, first is
			   "ibm,rgmii-CHIP" where CHIP is the host ASIC (like
			   EMAC) and the second is "ibm,rgmii".
                           For Axon, "ibm,rgmii-axon","ibm,rgmii"
    - reg                : <registers mapping>
    - revision           : as provided by the RGMII new version register if
			   available.
			   For Axon: 0x0000012a

   o) Xilinx IP cores

   The Xilinx EDK toolchain ships with a set of IP cores (devices) for use
   in Xilinx Spartan and Virtex FPGAs.  The devices cover the whole range
   of standard device types (network, serial, etc.) and miscellanious
   devices (gpio, LCD, spi, etc).  Also, since these devices are
   implemented within the fpga fabric every instance of the device can be
   synthesised with different options that change the behaviour.

   Each IP-core has a set of parameters which the FPGA designer can use to
   control how the core is synthesized.  Historically, the EDK tool would
   extract the device parameters relevant to device drivers and copy them
   into an 'xparameters.h' in the form of #define symbols.  This tells the
   device drivers how the IP cores are configured, but it requres the kernel
   to be recompiled every time the FPGA bitstream is resynthesized.

   The new approach is to export the parameters into the device tree and
   generate a new device tree each time the FPGA bitstream changes.  The
   parameters which used to be exported as #defines will now become
   properties of the device node.  In general, device nodes for IP-cores
   will take the following form:

	(name): (generic-name)@(base-address) {
		compatible = "xlnx,(ip-core-name)-(HW_VER)"
			     [, (list of compatible devices), ...];
		reg = <(baseaddr) (size)>;
		interrupt-parent = <&interrupt-controller-phandle>;
		interrupts = < ... >;
		xlnx,(parameter1) = "(string-value)";
		xlnx,(parameter2) = <(int-value)>;
	};

	(generic-name):   an open firmware-style name that describes the
			generic class of device.  Preferably, this is one word, such
			as 'serial' or 'ethernet'.
	(ip-core-name):	the name of the ip block (given after the BEGIN
			directive in system.mhs).  Should be in lowercase
			and all underscores '_' converted to dashes '-'.
	(name):		is derived from the "PARAMETER INSTANCE" value.
	(parameter#):	C_* parameters from system.mhs.  The C_ prefix is
			dropped from the parameter name, the name is converted
			to lowercase and all underscore '_' characters are
			converted to dashes '-'.
	(baseaddr):	the baseaddr parameter value (often named C_BASEADDR).
	(HW_VER):	from the HW_VER parameter.
	(size):		the address range size (often C_HIGHADDR - C_BASEADDR + 1).

   Typically, the compatible list will include the exact IP core version
   followed by an older IP core version which implements the same
   interface or any other device with the same interface.

   'reg', 'interrupt-parent' and 'interrupts' are all optional properties.

   For example, the following block from system.mhs:

	BEGIN opb_uartlite
		PARAMETER INSTANCE = opb_uartlite_0
		PARAMETER HW_VER = 1.00.b
		PARAMETER C_BAUDRATE = 115200
		PARAMETER C_DATA_BITS = 8
		PARAMETER C_ODD_PARITY = 0
		PARAMETER C_USE_PARITY = 0
		PARAMETER C_CLK_FREQ = 50000000
		PARAMETER C_BASEADDR = 0xEC100000
		PARAMETER C_HIGHADDR = 0xEC10FFFF
		BUS_INTERFACE SOPB = opb_7
		PORT OPB_Clk = CLK_50MHz
		PORT Interrupt = opb_uartlite_0_Interrupt
		PORT RX = opb_uartlite_0_RX
		PORT TX = opb_uartlite_0_TX
		PORT OPB_Rst = sys_bus_reset_0
	END

   becomes the following device tree node:

	opb_uartlite_0: serial@ec100000 {
		device_type = "serial";
		compatible = "xlnx,opb-uartlite-1.00.b";
		reg = <ec100000 10000>;
		interrupt-parent = <&opb_intc_0>;
		interrupts = <1 0>; // got this from the opb_intc parameters
		current-speed = <d#115200>;	// standard serial device prop
		clock-frequency = <d#50000000>;	// standard serial device prop
		xlnx,data-bits = <8>;
		xlnx,odd-parity = <0>;
		xlnx,use-parity = <0>;
	};

   Some IP cores actually implement 2 or more logical devices.  In
   this case, the device should still describe the whole IP core with
   a single node and add a child node for each logical device.  The
   ranges property can be used to translate from parent IP-core to the
   registers of each device.  In addition, the parent node should be
   compatible with the bus type 'xlnx,compound', and should contain
   #address-cells and #size-cells, as with any other bus.  (Note: this
   makes the assumption that both logical devices have the same bus
   binding.  If this is not true, then separate nodes should be used
   for each logical device).  The 'cell-index' property can be used to
   enumerate logical devices within an IP core.  For example, the
   following is the system.mhs entry for the dual ps2 controller found
   on the ml403 reference design.

	BEGIN opb_ps2_dual_ref
		PARAMETER INSTANCE = opb_ps2_dual_ref_0
		PARAMETER HW_VER = 1.00.a
		PARAMETER C_BASEADDR = 0xA9000000
		PARAMETER C_HIGHADDR = 0xA9001FFF
		BUS_INTERFACE SOPB = opb_v20_0
		PORT Sys_Intr1 = ps2_1_intr
		PORT Sys_Intr2 = ps2_2_intr
		PORT Clkin1 = ps2_clk_rx_1
		PORT Clkin2 = ps2_clk_rx_2
		PORT Clkpd1 = ps2_clk_tx_1
		PORT Clkpd2 = ps2_clk_tx_2
		PORT Rx1 = ps2_d_rx_1
		PORT Rx2 = ps2_d_rx_2
		PORT Txpd1 = ps2_d_tx_1
		PORT Txpd2 = ps2_d_tx_2
	END

   It would result in the following device tree nodes:

	opb_ps2_dual_ref_0: opb-ps2-dual-ref@a9000000 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "xlnx,compound";
		ranges = <0 a9000000 2000>;
		// If this device had extra parameters, then they would
		// go here.
		ps2@0 {
			compatible = "xlnx,opb-ps2-dual-ref-1.00.a";
			reg = <0 40>;
			interrupt-parent = <&opb_intc_0>;
			interrupts = <3 0>;
			cell-index = <0>;
		};
		ps2@1000 {
			compatible = "xlnx,opb-ps2-dual-ref-1.00.a";
			reg = <1000 40>;
			interrupt-parent = <&opb_intc_0>;
			interrupts = <3 0>;
			cell-index = <0>;
		};
	};

   Also, the system.mhs file defines bus attachments from the processor
   to the devices.  The device tree structure should reflect the bus
   attachments.  Again an example; this system.mhs fragment:

	BEGIN ppc405_virtex4
		PARAMETER INSTANCE = ppc405_0
		PARAMETER HW_VER = 1.01.a
		BUS_INTERFACE DPLB = plb_v34_0
		BUS_INTERFACE IPLB = plb_v34_0
	END

	BEGIN opb_intc
		PARAMETER INSTANCE = opb_intc_0
		PARAMETER HW_VER = 1.00.c
		PARAMETER C_BASEADDR = 0xD1000FC0
		PARAMETER C_HIGHADDR = 0xD1000FDF
		BUS_INTERFACE SOPB = opb_v20_0
	END

	BEGIN opb_uart16550
		PARAMETER INSTANCE = opb_uart16550_0
		PARAMETER HW_VER = 1.00.d
		PARAMETER C_BASEADDR = 0xa0000000
		PARAMETER C_HIGHADDR = 0xa0001FFF
		BUS_INTERFACE SOPB = opb_v20_0
	END

	BEGIN plb_v34
		PARAMETER INSTANCE = plb_v34_0
		PARAMETER HW_VER = 1.02.a
	END

	BEGIN plb_bram_if_cntlr
		PARAMETER INSTANCE = plb_bram_if_cntlr_0
		PARAMETER HW_VER = 1.00.b
		PARAMETER C_BASEADDR = 0xFFFF0000
		PARAMETER C_HIGHADDR = 0xFFFFFFFF
		BUS_INTERFACE SPLB = plb_v34_0
	END

	BEGIN plb2opb_bridge
		PARAMETER INSTANCE = plb2opb_bridge_0
		PARAMETER HW_VER = 1.01.a
		PARAMETER C_RNG0_BASEADDR = 0x20000000
		PARAMETER C_RNG0_HIGHADDR = 0x3FFFFFFF
		PARAMETER C_RNG1_BASEADDR = 0x60000000
		PARAMETER C_RNG1_HIGHADDR = 0x7FFFFFFF
		PARAMETER C_RNG2_BASEADDR = 0x80000000
		PARAMETER C_RNG2_HIGHADDR = 0xBFFFFFFF
		PARAMETER C_RNG3_BASEADDR = 0xC0000000
		PARAMETER C_RNG3_HIGHADDR = 0xDFFFFFFF
		BUS_INTERFACE SPLB = plb_v34_0
		BUS_INTERFACE MOPB = opb_v20_0
	END

   Gives this device tree (some properties removed for clarity):

	plb@0 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "xlnx,plb-v34-1.02.a";
		device_type = "ibm,plb";
		ranges; // 1:1 translation

		plb_bram_if_cntrl_0: bram@ffff0000 {
			reg = <ffff0000 10000>;
		}

		opb@20000000 {
			#address-cells = <1>;
			#size-cells = <1>;
			ranges = <20000000 20000000 20000000
				  60000000 60000000 20000000
				  80000000 80000000 40000000
				  c0000000 c0000000 20000000>;

			opb_uart16550_0: serial@a0000000 {
				reg = <a00000000 2000>;
			};

			opb_intc_0: interrupt-controller@d1000fc0 {
				reg = <d1000fc0 20>;
			};
		};
	};

   That covers the general approach to binding xilinx IP cores into the
   device tree.  The following are bindings for specific devices:

      i) Xilinx ML300 Framebuffer

      Simple framebuffer device from the ML300 reference design (also on the
      ML403 reference design as well as others).

      Optional properties:
       - resolution = <xres yres> : pixel resolution of framebuffer.  Some
                                    implementations use a different resolution.
                                    Default is <d#640 d#480>
       - virt-resolution = <xvirt yvirt> : Size of framebuffer in memory.
                                           Default is <d#1024 d#480>.
       - rotate-display (empty) : rotate display 180 degrees.

      ii) Xilinx SystemACE

      The Xilinx SystemACE device is used to program FPGAs from an FPGA
      bitstream stored on a CF card.  It can also be used as a generic CF
      interface device.

      Optional properties:
       - 8-bit (empty) : Set this property for SystemACE in 8 bit mode

      iii) Xilinx EMAC and Xilinx TEMAC

      Xilinx Ethernet devices.  In addition to general xilinx properties
      listed above, nodes for these devices should include a phy-handle
      property, and may include other common network device properties
      like local-mac-address.
      
      iv) Xilinx Uartlite

      Xilinx uartlite devices are simple fixed speed serial ports.

      Requred properties:
       - current-speed : Baud rate of uartlite

      v) Xilinx hwicap

		Xilinx hwicap devices provide access to the configuration logic
		of the FPGA through the Internal Configuration Access Port
		(ICAP).  The ICAP enables partial reconfiguration of the FPGA,
		readback of the configuration information, and some control over
		'warm boots' of the FPGA fabric.

		Required properties:
		- xlnx,family : The family of the FPGA, necessary since the
                      capabilities of the underlying ICAP hardware
                      differ between different families.  May be
                      'virtex2p', 'virtex4', or 'virtex5'.

    p) Freescale Synchronous Serial Interface

       The SSI is a serial device that communicates with audio codecs.  It can
       be programmed in AC97, I2S, left-justified, or right-justified modes.

       Required properties:
       - compatible	  : compatible list, containing "fsl,ssi"
       - cell-index	  : the SSI, <0> = SSI1, <1> = SSI2, and so on
       - reg		  : offset and length of the register set for the device
       - interrupts	  : <a b> where a is the interrupt number and b is a
                            field that represents an encoding of the sense and
			    level information for the interrupt.  This should be
			    encoded based on the information in section 2)
			    depending on the type of interrupt controller you
			    have.
       - interrupt-parent : the phandle for the interrupt controller that
                            services interrupts for this device.
       - fsl,mode	  : the operating mode for the SSI interface
			    "i2s-slave" - I2S mode, SSI is clock slave
			    "i2s-master" - I2S mode, SSI is clock master
			    "lj-slave" - left-justified mode, SSI is clock slave
			    "lj-master" - l.j. mode, SSI is clock master
			    "rj-slave" - right-justified mode, SSI is clock slave
			    "rj-master" - r.j., SSI is clock master
			    "ac97-slave" - AC97 mode, SSI is clock slave
			    "ac97-master" - AC97 mode, SSI is clock master

       Optional properties:
       - codec-handle	  : phandle to a 'codec' node that defines an audio
			    codec connected to this SSI.  This node is typically
			    a child of an I2C or other control node.

       Child 'codec' node required properties:
       - compatible	  : compatible list, contains the name of the codec

       Child 'codec' node optional properties:
       - clock-frequency  : The frequency of the input clock, which typically
                            comes from an on-board dedicated oscillator.

    * Freescale 83xx DMA Controller

    Freescale PowerPC 83xx have on chip general purpose DMA controllers.

    Required properties:

    - compatible        : compatible list, contains 2 entries, first is
			 "fsl,CHIP-dma", where CHIP is the processor
			 (mpc8349, mpc8360, etc.) and the second is
			 "fsl,elo-dma"
    - reg               : <registers mapping for DMA general status reg>
    - ranges 		: Should be defined as specified in 1) to describe the
			  DMA controller channels.
    - cell-index        : controller index.  0 for controller @ 0x8100
    - interrupts        : <interrupt mapping for DMA IRQ>
    - interrupt-parent  : optional, if needed for interrupt mapping


    - DMA channel nodes:
	    - compatible        : compatible list, contains 2 entries, first is
				 "fsl,CHIP-dma-channel", where CHIP is the processor
				 (mpc8349, mpc8350, etc.) and the second is
				 "fsl,elo-dma-channel"
	    - reg               : <registers mapping for channel>
	    - cell-index        : dma channel index starts at 0.

    Optional properties:
	    - interrupts        : <interrupt mapping for DMA channel IRQ>
				  (on 83xx this is expected to be identical to
				   the interrupts property of the parent node)
	    - interrupt-parent  : optional, if needed for interrupt mapping

  Example:
	dma@82a8 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "fsl,mpc8349-dma", "fsl,elo-dma";
		reg = <82a8 4>;
		ranges = <0 8100 1a4>;
		interrupt-parent = <&ipic>;
		interrupts = <47 8>;
		cell-index = <0>;
		dma-channel@0 {
			compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel";
			cell-index = <0>;
			reg = <0 80>;
		};
		dma-channel@80 {
			compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel";
			cell-index = <1>;
			reg = <80 80>;
		};
		dma-channel@100 {
			compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel";
			cell-index = <2>;
			reg = <100 80>;
		};
		dma-channel@180 {
			compatible = "fsl,mpc8349-dma-channel", "fsl,elo-dma-channel";
			cell-index = <3>;
			reg = <180 80>;
		};
	};

   * Freescale 85xx/86xx DMA Controller

    Freescale PowerPC 85xx/86xx have on chip general purpose DMA controllers.

    Required properties:

    - compatible        : compatible list, contains 2 entries, first is
			 "fsl,CHIP-dma", where CHIP is the processor
			 (mpc8540, mpc8540, etc.) and the second is
			 "fsl,eloplus-dma"
    - reg               : <registers mapping for DMA general status reg>
    - cell-index        : controller index.  0 for controller @ 0x21000,
                                             1 for controller @ 0xc000
    - ranges 		: Should be defined as specified in 1) to describe the
			  DMA controller channels.

    - DMA channel nodes:
	    - compatible        : compatible list, contains 2 entries, first is
				 "fsl,CHIP-dma-channel", where CHIP is the processor
				 (mpc8540, mpc8560, etc.) and the second is
				 "fsl,eloplus-dma-channel"
	    - cell-index        : dma channel index starts at 0.
	    - reg               : <registers mapping for channel>
	    - interrupts        : <interrupt mapping for DMA channel IRQ>
	    - interrupt-parent  : optional, if needed for interrupt mapping

  Example:
	dma@21300 {
		#address-cells = <1>;
		#size-cells = <1>;
		compatible = "fsl,mpc8540-dma", "fsl,eloplus-dma";
		reg = <21300 4>;
		ranges = <0 21100 200>;
		cell-index = <0>;
		dma-channel@0 {
			compatible = "fsl,mpc8540-dma-channel", "fsl,eloplus-dma-channel";
			reg = <0 80>;
			cell-index = <0>;
			interrupt-parent = <&mpic>;
			interrupts = <14 2>;
		};
		dma-channel@80 {
			compatible = "fsl,mpc8540-dma-channel", "fsl,eloplus-dma-channel";
			reg = <80 80>;
			cell-index = <1>;
			interrupt-parent = <&mpic>;
			interrupts = <15 2>;
		};
		dma-channel@100 {
			compatible = "fsl,mpc8540-dma-channel", "fsl,eloplus-dma-channel";
			reg = <100 80>;
			cell-index = <2>;
			interrupt-parent = <&mpic>;
			interrupts = <16 2>;
		};
		dma-channel@180 {
			compatible = "fsl,mpc8540-dma-channel", "fsl,eloplus-dma-channel";
			reg = <180 80>;
			cell-index = <3>;
			interrupt-parent = <&mpic>;
			interrupts = <17 2>;
		};
	};

    * Freescale 8xxx/3.0 Gb/s SATA nodes

    SATA nodes are defined to describe on-chip Serial ATA controllers.
    Each SATA port should have its own node.

    Required properties:
    - compatible        : compatible list, contains 2 entries, first is
			 "fsl,CHIP-sata", where CHIP is the processor
			 (mpc8315, mpc8379, etc.) and the second is
			 "fsl,pq-sata"
    - interrupts        : <interrupt mapping for SATA IRQ>
    - cell-index        : controller index.
                              1 for controller @ 0x18000
                              2 for controller @ 0x19000
                              3 for controller @ 0x1a000
                              4 for controller @ 0x1b000

    Optional properties:
    - interrupt-parent  : optional, if needed for interrupt mapping
    - reg               : <registers mapping>

   Example:

	sata@18000 {
		compatible = "fsl,mpc8379-sata", "fsl,pq-sata";
		reg = <0x18000 0x1000>;
		cell-index = <1>;
		interrupts = <2c 8>;
		interrupt-parent = < &ipic >;
        };

    q) USB EHCI controllers

    Required properties:
      - compatible : should be "usb-ehci".
      - reg : should contain at least address and length of the standard EHCI
        register set for the device. Optional platform-dependent registers
        (debug-port or other) can be also specified here, but only after
        definition of standard EHCI registers.
      - interrupts : one EHCI interrupt should be described here.
    If device registers are implemented in big endian mode, the device
    node should have "big-endian-regs" property.
    If controller implementation operates with big endian descriptors,
    "big-endian-desc" property should be specified.
    If both big endian registers and descriptors are used by the controller
    implementation, "big-endian" property can be specified instead of having
    both "big-endian-regs" and "big-endian-desc".

     Example (Sequoia 440EPx):
	    ehci@e0000300 {
		   compatible = "ibm,usb-ehci-440epx", "usb-ehci";
		   interrupt-parent = <&UIC0>;
		   interrupts = <1a 4>;
		   reg = <0 e0000300 90 0 e0000390 70>;
		   big-endian;
	   };


   More devices will be defined as this spec matures.

VII - Specifying interrupt information for devices
===================================================

The device tree represents the busses and devices of a hardware
system in a form similar to the physical bus topology of the
hardware.

In addition, a logical 'interrupt tree' exists which represents the
hierarchy and routing of interrupts in the hardware.

The interrupt tree model is fully described in the
document "Open Firmware Recommended Practice: Interrupt
Mapping Version 0.9".  The document is available at:
<http://playground.sun.com/1275/practice>.

1) interrupts property
----------------------

Devices that generate interrupts to a single interrupt controller
should use the conventional OF representation described in the
OF interrupt mapping documentation.

Each device which generates interrupts must have an 'interrupt'
property.  The interrupt property value is an arbitrary number of
of 'interrupt specifier' values which describe the interrupt or
interrupts for the device.

The encoding of an interrupt specifier is determined by the
interrupt domain in which the device is located in the
interrupt tree.  The root of an interrupt domain specifies in
its #interrupt-cells property the number of 32-bit cells
required to encode an interrupt specifier.  See the OF interrupt
mapping documentation for a detailed description of domains.

For example, the binding for the OpenPIC interrupt controller
specifies  an #interrupt-cells value of 2 to encode the interrupt
number and level/sense information. All interrupt children in an
OpenPIC interrupt domain use 2 cells per interrupt in their interrupts
property.

The PCI bus binding specifies a #interrupt-cell value of 1 to encode
which interrupt pin (INTA,INTB,INTC,INTD) is used.

2) interrupt-parent property
----------------------------

The interrupt-parent property is specified to define an explicit
link between a device node and its interrupt parent in
the interrupt tree.  The value of interrupt-parent is the
phandle of the parent node.

If the interrupt-parent property is not defined for a node, it's
interrupt parent is assumed to be an ancestor in the node's
_device tree_ hierarchy.

3) OpenPIC Interrupt Controllers
--------------------------------

OpenPIC interrupt controllers require 2 cells to encode
interrupt information.  The first cell defines the interrupt
number.  The second cell defines the sense and level
information.

Sense and level information should be encoded as follows:

	0 = low to high edge sensitive type enabled
	1 = active low level sensitive type enabled
	2 = active high level sensitive type enabled
	3 = high to low edge sensitive type enabled

4) ISA Interrupt Controllers
----------------------------

ISA PIC interrupt controllers require 2 cells to encode
interrupt information.  The first cell defines the interrupt
number.  The second cell defines the sense and level
information.

ISA PIC interrupt controllers should adhere to the ISA PIC
encodings listed below:

	0 =  active low level sensitive type enabled
	1 =  active high level sensitive type enabled
	2 =  high to low edge sensitive type enabled
	3 =  low to high edge sensitive type enabled


Appendix A - Sample SOC node for MPC8540
========================================

Note that the #address-cells and #size-cells for the SoC node
in this example have been explicitly listed; these are likely
not necessary as they are usually the same as the root node.

	soc8540@e0000000 {
		#address-cells = <1>;
		#size-cells = <1>;
		#interrupt-cells = <2>;
		device_type = "soc";
		ranges = <00000000 e0000000 00100000>
		reg = <e0000000 00003000>;
		bus-frequency = <0>;

		mdio@24520 {
			reg = <24520 20>;
			device_type = "mdio";
			compatible = "gianfar";

			ethernet-phy@0 {
				linux,phandle = <2452000>
				interrupt-parent = <40000>;
				interrupts = <35 1>;
				reg = <0>;
				device_type = "ethernet-phy";
			};

			ethernet-phy@1 {
				linux,phandle = <2452001>
				interrupt-parent = <40000>;
				interrupts = <35 1>;
				reg = <1>;
				device_type = "ethernet-phy";
			};

			ethernet-phy@3 {
				linux,phandle = <2452002>
				interrupt-parent = <40000>;
				interrupts = <35 1>;
				reg = <3>;
				device_type = "ethernet-phy";
			};

		};

		ethernet@24000 {
			#size-cells = <0>;
			device_type = "network";
			model = "TSEC";
			compatible = "gianfar";
			reg = <24000 1000>;
			mac-address = [ 00 E0 0C 00 73 00 ];
			interrupts = <d 3 e 3 12 3>;
			interrupt-parent = <40000>;
			phy-handle = <2452000>;
		};

		ethernet@25000 {
			#address-cells = <1>;
			#size-cells = <0>;
			device_type = "network";
			model = "TSEC";
			compatible = "gianfar";
			reg = <25000 1000>;
			mac-address = [ 00 E0 0C 00 73 01 ];
			interrupts = <13 3 14 3 18 3>;
			interrupt-parent = <40000>;
			phy-handle = <2452001>;
		};

		ethernet@26000 {
			#address-cells = <1>;
			#size-cells = <0>;
			device_type = "network";
			model = "FEC";
			compatible = "gianfar";
			reg = <26000 1000>;
			mac-address = [ 00 E0 0C 00 73 02 ];
			interrupts = <19 3>;
			interrupt-parent = <40000>;
			phy-handle = <2452002>;
		};

		serial@4500 {
			device_type = "serial";
			compatible = "ns16550";
			reg = <4500 100>;
			clock-frequency = <0>;
			interrupts = <1a 3>;
			interrupt-parent = <40000>;
		};

		pic@40000 {
			linux,phandle = <40000>;
			clock-frequency = <0>;
			interrupt-controller;
			#address-cells = <0>;
			reg = <40000 40000>;
			built-in;
			compatible = "chrp,open-pic";
			device_type = "open-pic";
                        big-endian;
		};

		i2c@3000 {
			interrupt-parent = <40000>;
			interrupts = <1b 3>;
			reg = <3000 18>;
			device_type = "i2c";
			compatible  = "fsl-i2c";
			dfsrr;
		};

	};