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

Since 2017, there is an space reserved for userspace API,
created by changeset 1d596dee38 ("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>

Documentation/userspace-api/media/rc/lirc-func.rst

@@ -0,0 +1,34 @@
+.. 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
+
+.. _lirc_func:
+
+LIRC Function Reference
+=======================
+
+
+.. toctree::
+    :maxdepth: 1
+
+    lirc-read
+    lirc-write
+    lirc-get-features
+    lirc-get-send-mode
+    lirc-get-rec-mode
+    lirc-get-rec-resolution
+    lirc-set-send-duty-cycle
+    lirc-get-timeout
+    lirc-set-rec-timeout
+    lirc-set-rec-carrier
+    lirc-set-rec-carrier-range
+    lirc-set-send-carrier
+    lirc-set-transmitter-mask
+    lirc-set-rec-timeout-reports
+    lirc-set-measure-carrier-mode
+    lirc-set-wideband-receiver