media: docs: make V4L documents more compatible with Sphinx 3.1+

Sphinx 3.x broke support for the cdomain.py extension, as the
c domain code was rewritten. Due to that, the c tags need to
be re-written, in order to use the new c domain notation.

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

Documentation/userspace-api/media/v4l/format.rst

@@ -1,4 +1,5 @@
 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
 
 .. _format:
 
@@ -6,7 +7,6 @@
 Data Formats
 ************
 
-
 Data Format Negotiation
 =======================
 
@@ -53,8 +53,8 @@ image size.
 When applications omit the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl its locking side
 effects are implied by the next step, the selection of an I/O method
 with the :ref:`VIDIOC_REQBUFS` ioctl or implicit
-with the first :ref:`read() <func-read>` or
-:ref:`write() <func-write>` call.
+with the first :c:func:`read()` or
+:c:func:`write()` call.
 
 Generally only one logical stream can be assigned to a file descriptor,
 the exception being drivers permitting simultaneous video capturing and
@@ -67,7 +67,6 @@ All drivers exchanging data with applications must support the
 :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. Implementation of the
 :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` is highly recommended but optional.
 
-
 Image Format Enumeration
 ========================