diff --git a/Documentation/md.txt b/Documentation/md.txt
index c5512af..fd43fd2 100644
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -189,6 +189,14 @@
      1.2 (newer format in varying locations) or "none" indicating that
      the kernel isn't managing metadata at all.
 
+  level
+     The raid 'level' for this array.  The name will often (but not
+     always) be the same as the name of the module that implements the
+     level.  To be auto-loaded the module must have an alias
+        md-$LEVEL  e.g. md-raid5
+     This can be written only while the array is being assembled, not
+     after it is started.
+
 As component devices are added to an md array, they appear in the 'md'
 directory as new directories named
       dev-XXX