This documentation was inadvertently released under the CC-BY-SA-4.0
license. It was intended to be released under GPL-2.0 or later.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Move the idr kernel-doc to its own idr.rst file and add a few
paragraphs about how to use it. Also add some more kernel-doc.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>