scripts: kernel-doc: Translate the DESCRIPTION section

Transition the description section into POD. This is one of the standard
documentation sections. This adjustment makes the section available for
POD and makes it look better.

Notes:
- an article addition
- paragraphing correction

Signed-off-by: Tomasz Warniełło <tomasz.warniello@gmail.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Disliked-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/r/20220218181628.1411551-4-tomasz.warniello@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

scripts/kernel-doc

@@ -41,6 +41,15 @@ kernel-doc - Print formatted kernel documentation to stdout
 
 Run `kernel-doc -h` for details.
 
+=head1 DESCRIPTION
+
+Read C language source or header FILEs, extract embedded documentation comments,
+and print formatted documentation to standard output.
+
+The documentation comments are identified by the "/**" opening comment mark.
+
+See Documentation/doc-guide/kernel-doc.rst for the documentation comment syntax.
+
 =cut
 
 # 18/01/2001 - 	Cleanups
@@ -72,12 +81,6 @@ sub usage {
     my $message = <<"EOF";
 Usage: $0 [OPTION ...] FILE ...
 
-Read C language source or header FILEs, extract embedded documentation comments,
-and print formatted documentation to standard output.
-
-The documentation comments are identified by "/**" opening comment mark. See
-Documentation/doc-guide/kernel-doc.rst for the documentation comment syntax.
-
 Output format selection (mutually exclusive):
   -man			Output troff manual page format. This is the default.
   -rst			Output reStructuredText format.