This struct is mentioned at the kAPI docbook. So, let's document
it.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

Reorganize the order of the document, putting the chapters
on a more logical order and renaming some sections.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>