doc-rst: define PDF's of the media folder

To build only the PDF of the media folder run::

  make SPHINXDIRS=media pdfdocs
Signed-off-by: NMarkus Heiser <markus.heiser@darmarIT.de>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/media/conf.py

@@ -3,3 +3,8 @@
 project = 'Linux Media Subsystem Documentation'
 
 tags.add("subproject")
+
+latex_documents = [
+    ('index', 'media.tex', 'Linux Media Subsystem Documentation',
+     'The kernel development community', 'manual'),
+]