7 files changed, 132 insertions, 17 deletions
diff --git a/Documentation/Makefile b/Documentation/Makefile
index 79ecee62d597..cc786d11a028 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -2,7 +2,8 @@
 # Makefile for Sphinx documentation
 #
 
-subdir-y := devicetree/bindings/
+# for cleaning
+subdir- := devicetree/bindings
 
 # Check for broken documentation file references
 ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)
diff --git a/Documentation/devicetree/bindings/.gitignore b/Documentation/devicetree/bindings/.gitignore
index ef82fcfcccab..57afa1533a5f 100644
--- a/Documentation/devicetree/bindings/.gitignore
+++ b/Documentation/devicetree/bindings/.gitignore
@@ -1,2 +1,2 @@
 *.example.dts
-processed-schema.yaml
+processed-schema*.yaml
diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
index 646cb3525373..1df680d07461 100644
--- a/Documentation/devicetree/bindings/Makefile
+++ b/Documentation/devicetree/bindings/Makefile
@@ -2,7 +2,6 @@
 DT_DOC_CHECKER ?= dt-doc-validate
 DT_EXTRACT_EX ?= dt-extract-example
 DT_MK_SCHEMA ?= dt-mk-schema
-DT_MK_SCHEMA_FLAGS := $(if $(DT_SCHEMA_FILES), -u)
 
 quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
       cmd_chk_binding = $(DT_DOC_CHECKER) -u $(srctree)/$(src) $< ; \
@@ -11,26 +10,35 @@ quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
 $(obj)/%.example.dts: $(src)/%.yaml FORCE
 	$(call if_changed,chk_binding)
 
-DT_TMP_SCHEMA := processed-schema.yaml
+# Use full schemas when checking %.example.dts
+DT_TMP_SCHEMA := $(obj)/processed-schema-examples.yaml
 
 quiet_cmd_mk_schema = SCHEMA  $@
       cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(real-prereqs)
 
-DT_DOCS = $(shell \
+DT_DOCS = $(addprefix $(src)/, \
+	$(shell \
 	cd $(srctree)/$(src) && \
 	find * \( -name '*.yaml' ! \
-		-name $(DT_TMP_SCHEMA) ! \
+		-name 'processed-schema*' ! \
 		-name '*.example.dt.yaml' \) \
-	)
+	))
 
-DT_SCHEMA_FILES ?= $(addprefix $(src)/,$(DT_DOCS))
+DT_SCHEMA_FILES ?= $(DT_DOCS)
 
-ifeq ($(CHECK_DTBS),)
-extra-y += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
-extra-y += $(patsubst $(src)/%.yaml,%.example.dt.yaml, $(DT_SCHEMA_FILES))
-endif
+extra-$(CHECK_DT_BINDING) += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
+extra-$(CHECK_DT_BINDING) += $(patsubst $(src)/%.yaml,%.example.dt.yaml, $(DT_SCHEMA_FILES))
+extra-$(CHECK_DT_BINDING) += processed-schema-examples.yaml
 
-$(obj)/$(DT_TMP_SCHEMA): $(DT_SCHEMA_FILES) FORCE
+override DTC_FLAGS := \
+	-Wno-avoid_unnecessary_addr_size \
+	-Wno-graph_child_address
+
+$(obj)/processed-schema-examples.yaml: $(DT_DOCS) FORCE
+	$(call if_changed,mk_schema)
+
+$(obj)/processed-schema.yaml: DT_MK_SCHEMA_FLAGS := -u
+$(obj)/processed-schema.yaml: $(DT_SCHEMA_FILES) FORCE
 	$(call if_changed,mk_schema)
 
-extra-y += $(DT_TMP_SCHEMA)
+extra-y += processed-schema.yaml
diff --git a/Documentation/devicetree/writing-schema.rst b/Documentation/devicetree/writing-schema.rst
index 7635ab230456..220cf464ed77 100644
--- a/Documentation/devicetree/writing-schema.rst
+++ b/Documentation/devicetree/writing-schema.rst
@@ -147,6 +147,10 @@ Note that ``dtbs_check`` will skip any binding schema files with errors. It is
 necessary to use ``dt_binding_check`` to get all the validation errors in the
 binding schema files.
 
+It is possible to run both in a single command::
+
+    make dt_binding_check dtbs_check
+
 It is also possible to run checks with a single schema file by setting the
 ``DT_SCHEMA_FILES`` variable to a specific schema file.
 
diff --git a/Documentation/kbuild/index.rst b/Documentation/kbuild/index.rst
index 82daf2efcb73..cee2f99f734b 100644
--- a/Documentation/kbuild/index.rst
+++ b/Documentation/kbuild/index.rst
@@ -20,6 +20,7 @@ Kernel Build System
     issues
     reproducible-builds
     gcc-plugins
+    llvm
 
 .. only::  subproject and html
 
diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
index d0111dd26410..a1601ec3317b 100644
--- a/Documentation/kbuild/kconfig-language.rst
+++ b/Documentation/kbuild/kconfig-language.rst
@@ -159,11 +159,11 @@ applicable everywhere (see syntax).
   Given the following example::
 
     config FOO
-	tristate
+	tristate "foo"
 	imply BAZ
 
     config BAZ
-	tristate
+	tristate "baz"
 	depends on BAR
 
   The following values are possible:
@@ -173,7 +173,10 @@ applicable everywhere (see syntax).
 	===		===		=============	==============
 	n		y		n		N/m/y
 	m		y		m		M/y/n
-	y		y		y		Y/n
+	y		y		y		Y/m/n
+	n		m		n		N/m
+	m		m		m		M/n
+	y		m		n		M/n
 	y		n		*		N
 	===		===		=============	==============
 
@@ -181,6 +184,24 @@ applicable everywhere (see syntax).
   ability to hook into a secondary subsystem while allowing the user to
   configure that subsystem out without also having to unset these drivers.
 
+  Note: If the combination of FOO=y and BAR=m causes a link error,
+  you can guard the function call with IS_REACHABLE()::
+
+	foo_init()
+	{
+		if (IS_REACHABLE(CONFIG_BAZ))
+			baz_register(&foo);
+		...
+	}
+
+  Note: If the feature provided by BAZ is highly desirable for FOO,
+  FOO should imply not only BAZ, but also its dependency BAR::
+
+    config FOO
+	tristate "foo"
+	imply BAR
+	imply BAZ
+
 - limiting menu display: "visible if" <expr>
 
   This attribute is only applicable to menu blocks, if the condition is
diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst
new file mode 100644
index 000000000000..d6c79eb4e23e
--- /dev/null
+++ b/Documentation/kbuild/llvm.rst
@@ -0,0 +1,80 @@
+==============================
+Building Linux with Clang/LLVM
+==============================
+
+This document covers how to build the Linux kernel with Clang and LLVM
+utilities.
+
+About
+-----
+
+The Linux kernel has always traditionally been compiled with GNU toolchains
+such as GCC and binutils. Ongoing work has allowed for `Clang
+<https://clang.llvm.org/>`_ and `LLVM <https://llvm.org/>`_ utilities to be
+used as viable substitutes. Distributions such as `Android
+<https://www.android.com/>`_, `ChromeOS
+<https://www.chromium.org/chromium-os>`_, and `OpenMandriva
+<https://www.openmandriva.org/>`_ use Clang built kernels.  `LLVM is a
+collection of toolchain components implemented in terms of C++ objects
+<https://www.aosabook.org/en/llvm.html>`_. Clang is a front-end to LLVM that
+supports C and the GNU C extensions required by the kernel, and is pronounced
+"klang," not "see-lang."
+
+Clang
+-----
+
+The compiler used can be swapped out via `CC=` command line argument to `make`.
+`CC=` should be set when selecting a config and during a build.
+
+	make CC=clang defconfig
+
+	make CC=clang
+
+Cross Compiling
+---------------
+
+A single Clang compiler binary will typically contain all supported backends,
+which can help simplify cross compiling.
+
+	ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang
+
+`CROSS_COMPILE` is not used to prefix the Clang compiler binary, instead
+`CROSS_COMPILE` is used to set a command line flag: `--target <triple>`. For
+example:
+
+	clang --target aarch64-linux-gnu foo.c
+
+LLVM Utilities
+--------------
+
+LLVM has substitutes for GNU binutils utilities. These can be invoked as
+additional parameters to `make`.
+
+	make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
+	  OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-objsize \\
+	  READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
+	  HOSTLD=ld.lld
+
+Getting Help
+------------
+
+- `Website <https://clangbuiltlinux.github.io/>`_
+- `Mailing List <https://groups.google.com/forum/#!forum/clang-built-linux>`_: <clang-built-linux@googlegroups.com>
+- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_
+- IRC: #clangbuiltlinux on chat.freenode.net
+- `Telegram <https://t.me/ClangBuiltLinux>`_: @ClangBuiltLinux
+- `Wiki <https://github.com/ClangBuiltLinux/linux/wiki>`_
+- `Beginner Bugs <https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22>`_
+
+Getting LLVM
+-------------
+
+- http://releases.llvm.org/download.html
+- https://github.com/llvm/llvm-project
+- https://llvm.org/docs/GettingStarted.html
+- https://llvm.org/docs/CMake.html
+- https://apt.llvm.org/
+- https://www.archlinux.org/packages/extra/x86_64/llvm/
+- https://github.com/ClangBuiltLinux/tc-build
+- https://github.com/ClangBuiltLinux/linux/wiki/Building-Clang-from-source
+- https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/