docs: */index.rst: Add newer documents to their respective index.rst

A number of new docs were added, but they're currently not on
the index.rst from the session they're supposed to be, causing
Sphinx warnings.

Add them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>