media: docs: move uAPI book to userspace-api/media

Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee3862 ("docs: Create a user-space API guide").

As the media subsystem was one of the first subsystems to use
Sphinx, until this patch, we were keeping things on a separate
place.

Let's just use the new location, as having all uAPI altogether
will likely make things easier for developers.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/Documentation/userspace-api/media/dvb/ca-set-descr.rst b/Documentation/userspace-api/media/dvb/ca-set-descr.rst
new file mode 100644
index 000000000000..2c57371675e2
--- /dev/null
+++ b/Documentation/userspace-api/media/dvb/ca-set-descr.rst
@@ -0,0 +1,53 @@
+.. Permission is granted to copy, distribute and/or modify this
+.. document under the terms of the GNU Free Documentation License,
+.. Version 1.1 or any later version published by the Free Software
+.. Foundation, with no Invariant Sections, no Front-Cover Texts
+.. and no Back-Cover Texts. A copy of the license is included at
+.. Documentation/userspace-api/media/fdl-appendix.rst.
+..
+.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
+
+.. _CA_SET_DESCR:
+
+============
+CA_SET_DESCR
+============
+
+Name
+----
+
+CA_SET_DESCR
+
+
+Synopsis
+--------
+
+.. c:function:: int ioctl(fd, CA_SET_DESCR, struct ca_descr *desc)
+    :name: CA_SET_DESCR
+
+
+Arguments
+---------
+
+``fd``
+  File descriptor returned by a previous call to :c:func:`open() <cec-open>`.
+
+``msg``
+  Pointer to struct :c:type:`ca_descr`.
+
+Description
+-----------
+
+CA_SET_DESCR is used for feeding descrambler CA slots with descrambling
+keys (referred as control words).
+
+Return Value
+------------
+
+On success 0 is returned.
+
+On error -1 is returned, and the ``errno`` variable is set
+appropriately.
+
+Generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.