media: docs: make DVB 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/dvb/fe-get-frontend.rst

@@ -1,4 +1,5 @@
 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: DTV.fe
 
 .. _FE_GET_FRONTEND:
 
@@ -13,32 +14,28 @@ FE_GET_FRONTEND
 
 .. attention:: This ioctl is deprecated.
 
-
 Synopsis
 ========
 
-.. c:function:: int ioctl(int fd, FE_GET_FRONTEND, struct dvb_frontend_parameters *p)
-    :name: FE_GET_FRONTEND
+.. c:macro:: FE_GET_FRONTEND
 
+``int ioctl(int fd, FE_GET_FRONTEND, struct dvb_frontend_parameters *p)``
 
 Arguments
 =========
 
 ``fd``
-    File descriptor returned by :c:func:`open() <dvb-fe-open>`.
-
+    File descriptor returned by :c:func:`open()`.
 
 ``p``
     Points to parameters for tuning operation.
 
-
 Description
 ===========
 
 This ioctl call queries the currently effective frontend parameters. For
 this command, read-only access to the device is sufficient.
 
-
 Return Value
 ============
 
@@ -51,7 +48,6 @@ appropriately.
     :header-rows:  0
     :stub-columns: 0
 
-
     -  .. row 1
 
        -  ``EINVAL``