documentation: how to use DOC: section blocks

Add info on how to use DOC: sections in kernel-doc.  DOC: sections enable
the addition of inline source file comments that are general in nature
instead of being specific to a function, struct, union, enum, or typedef.
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/kernel-doc-nano-HOWTO.txt

@@ -287,6 +287,32 @@ struct my_struct {
 };
 
 
+Including documentation blocks in source files
+----------------------------------------------
+
+To facilitate having source code and comments close together, you can
+include kernel-doc documentation blocks that are free-form comments
+instead of being kernel-doc for functions, structures, unions,
+enums, or typedefs.  This could be used for something like a
+theory of operation for a driver or library code, for example.
+
+This is done by using a DOC: section keyword with a section title.  E.g.:
+
+/**
+ * DOC: Theory of Operation
+ *
+ * The whizbang foobar is a dilly of a gizmo.  It can do whatever you
+ * want it to do, at any time.  It reads your mind.  Here's how it works.
+ *
+ * foo bar splat
+ *
+ * The only drawback to this gizmo is that is can sometimes damage
+ * hardware, software, or its subject(s).
+ */
+
+DOC: sections are used in SGML templates files as indicated below.
+
+
 How to make new SGML template files
 -----------------------------------
 
@@ -307,6 +333,9 @@ exported using EXPORT_SYMBOL.
 !F<filename> <function [functions...]> is replaced by the
 documentation, in <filename>, for the functions listed.
 
+!P<filename> <section title> is replaced by the contents of the DOC:
+section titled <section title> from <filename>.
+Spaces are allowed in <section title>; do not quote the <section title>.
 
 Tim.
 */ <twaugh@redhat.com>