diff --git a/[refs] b/[refs]
index 0376d245a3c9..af72c08ab592 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a47653fc2643cf61bcabba8c9ff5c45517c089ba
+refs/heads/master: 0f44cd23a5a2e26191a28ab6e91bd0c7849c8e0f
diff --git a/trunk/Documentation/SubmittingPatches b/trunk/Documentation/SubmittingPatches
index d91125ab6f49..0958e97d4bf4 100644
--- a/trunk/Documentation/SubmittingPatches
+++ b/trunk/Documentation/SubmittingPatches
@@ -340,8 +340,32 @@ now, but you can do this to mark internal company procedures or just
 point out some special detail about the sign-off. 
 
 
+13) When to use Acked-by:
 
-13) The canonical patch format
+The Signed-off-by: tag indicates that the signer was involved in the
+development of the patch, or that he/she was in the patch's delivery path.
+
+If a person was not directly involved in the preparation or handling of a
+patch but wishes to signify and record their approval of it then they can
+arrange to have an Acked-by: line added to the patch's changelog.
+
+Acked-by: is often used by the maintainer of the affected code when that
+maintainer neither contributed to nor forwarded the patch.
+
+Acked-by: is not as formal as Signed-off-by:.  It is a record that the acker
+has at least reviewed the patch and has indicated acceptance.  Hence patch
+mergers will sometimes manually convert an acker's "yep, looks good to me"
+into an Acked-by:.
+
+Acked-by: does not necessarily indicate acknowledgement of the entire patch.
+For example, if a patch affects multiple subsystems and has an Acked-by: from
+one subsystem maintainer then this usually indicates acknowledgement of just
+the part which affects that maintainer's code.  Judgement should be used here.
+ When in doubt people should refer to the original discussion in the mailing
+list archives.
+
+
+14) The canonical patch format
 
 The canonical patch subject line is: