Merge branch 'mauro' into docs-next

Merge branch 'mauro' into docs-next

Mauro says (as he's cleaning up my mess):

This small series address a regression caused by a new patch at
docs-next (and at linux-next).

Before this patch, when a cross-reference to a chapter within the
documentation is needed, we had to add a markup like:

	.. _foo:

	foo
	===

This behavor is now different after this patch:

	79f4fc61ad95 ("docs: fix reference to core-api/namespaces.rst")

As a Sphinx extension now creates automatically a reference
like the above, without requiring any extra markup.

That, however, comes with a price: it is not possible anymore to have
two sections with the same name within the entire Kernel docs!

This causes thousands of warnings, as we have sections named
"introduction" on lots of places.

This series solve this regression by doing two changes:

1) The references are now prefixed by the document name. So,
   a file named "bar" would have the "foo" reference as "bar:foo".

2) It will only use the first two levels. The first one is (usually) the
   name of the document, and the second one the chapter name.

This solves almost all problems we have. Still, there are a few places
where we have two chapters at the same document with the
same name. The first patch addresses this problem.

The second patch limits the escope of the autosectionlabel.