Documentation: move sharedsubtrees.txt to filesystems/

This documentation is also vfs-related.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index 632fe3f..e68021c 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -82,6 +82,8 @@
 	- info on relay, for efficient streaming from kernel to user space.
 romfs.txt
 	- description of the ROMFS filesystem.
+sharedsubtree.txt
+	- a description of shared subtrees for namespaces.
 smbfs.txt
 	- info on using filesystems with the SMB protocol (Win 3.11 and NT).
 spufs.txt