docs: Add rbtree documentation to the core-api

This file is close enough to being in rst format that I didn't feel
the need to alter it in any way.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Michel Lespinasse <walken@google.com>
Link: https://lore.kernel.org/r/20200401173343.17472-1-willy@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/core-api/index.rst

@@ -35,6 +35,7 @@ Library functionality that is used throughout the kernel.
    xarray
    idr
    circular-buffers
+   rbtree
    generic-radix-tree
    packing
    timekeeping

include/linux/rbtree.h

@@ -11,7 +11,7 @@
   I know it's not the cleaner way,  but in C (not in C++) to get
   performances and genericity...
 
-  See Documentation/rbtree.txt for documentation and samples.
+  See Documentation/core-api/rbtree.rst for documentation and samples.
 */
 
 #ifndef	_LINUX_RBTREE_H

include/linux/rbtree_augmented.h

@@ -21,7 +21,7 @@
  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  * The rest are implementation details you are not expected to depend on.
  *
- * See Documentation/rbtree.txt for documentation and samples.
+ * See Documentation/core-api/rbtree.rst for documentation and samples.
  */
 
 struct rb_augment_callbacks {

lib/Kconfig

@@ -427,7 +427,7 @@ config INTERVAL_TREE
 
 	  See:
 
-		Documentation/rbtree.txt
+		Documentation/core-api/rbtree.rst
 
 	  for more information.
 

tools/include/linux/rbtree.h

@@ -11,7 +11,7 @@
   I know it's not the cleaner way,  but in C (not in C++) to get
   performances and genericity...
 
-  See Documentation/rbtree.txt for documentation and samples.
+  See Documentation/core-api/rbtree.rst for documentation and samples.
 */
 
 #ifndef __TOOLS_LINUX_PERF_RBTREE_H

tools/include/linux/rbtree_augmented.h

@@ -23,7 +23,7 @@
  * rb_insert_augmented() and rb_erase_augmented() are intended to be public.
  * The rest are implementation details you are not expected to depend on.
  *
- * See Documentation/rbtree.txt for documentation and samples.
+ * See Documentation/core-api/rbtree.rst for documentation and samples.
  */
 
 struct rb_augment_callbacks {