augmented rbtree: add comments for RB_DECLARE_CALLBACKS macro

augmented rbtree: add comments for RB_DECLARE_CALLBACKS macro

Patch series "make RB_DECLARE_CALLBACKS more generic", v3.

These changes are intended to make the RB_DECLARE_CALLBACKS macro more
generic (allowing the aubmented subtree information to be a struct instead
of a scalar).

I have verified the compiled lib/interval_tree.o and mm/mmap.o files to
check that they didn't change.  This held as expected for interval_tree.o;
mmap.o did have some changes which could be reverted by marking
__vma_link_rb as noinline.  I did not add such a change to the patchset; I
felt it was reasonable enough to leave the inlining decision up to the
compiler.

This patch (of 3):

Add a short comment summarizing the arguments to RB_DECLARE_CALLBACKS.
The arguments are also now capitalized.  This copies the style of the
INTERVAL_TREE_DEFINE macro.

No functional changes in this commit, only comments and capitalization.

Link: http://lkml.kernel.org/r/20190703040156.56953-2-walken@google.com
Signed-off-by: Michel Lespinasse <walken@google.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>