This patch addresses several issues pointed by Randy Dunlap
<rdunlap@xenotime.net> at changeset ece722c:

- In the generated index.html file, "media" is listed first, but it
  should be listed in alphabetical order, not first.

- The generated files are (hidden) in .tmpmedia/

- The link from the top-level index.html file to "media" is to
  media/index.html, but the file is actually in .tmpmedia/media/index.html

- Please build docs with and without using "O=builddir" and test that.

- Would it be possible for media to have its own Makefile instead of
  merging into this one?

Due to the way cleandocs target works, I had to rename the media DocBook
to media_api, otherwise cleandocs would remove the /media directory.

Thanks-to: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

The xmlto validation produced a number of errors that are now fixed.
Sadly, the DocBook/Makefile still adds --skip-validation to xmlto, so
these errors are missed during a normal compile.
Signed-off-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Create the following two ioctls and implement them at the media device
level to enumerate entities, pads and links.

- MEDIA_IOC_ENUM_ENTITIES: Enumerate entities and their properties
- MEDIA_IOC_ENUM_LINKS: Enumerate all pads and links for a given entity

Entity IDs can be non-contiguous. Userspace applications should
enumerate entities using the MEDIA_ENT_ID_FLAG_NEXT flag. When the flag
is set in the entity ID, the MEDIA_IOC_ENUM_ENTITIES will return the
next entity with an ID bigger than the requested one.

Only forward links that originate at one of the entity's source pads are
returned during the enumeration process.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>