docs: kernel-doc: update commands to generate man page

(1) The command to generate man pages is truncated in the pdf version
of the document.  Reformat the command into multiple lines to prevent
the truncation.

(2) Older versions of git do not support all variants of pathspec
syntax.  Provide commands to generate man pages for various
alternate syntax.
Signed-off-by: NFrank Rowand <frank.rowand@sony.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/doc-guide/kernel-doc.rst

@@ -517,4 +517,17 @@ How to use kernel-doc to generate man pages
 If you just want to use kernel-doc to generate man pages you can do this
 from the kernel git tree::
 
-  $ scripts/kernel-doc -man $(git grep -l '/\*\*' -- :^Documentation :^tools) | scripts/split-man.pl /tmp/man
+  $ scripts/kernel-doc -man \
+    $(git grep -l '/\*\*' -- :^Documentation :^tools) \
+    | scripts/split-man.pl /tmp/man
+
+Some older versions of git do not support some of the variants of syntax for
+path exclusion.  One of the following commands may work for those versions::
+
+  $ scripts/kernel-doc -man \
+    $(git grep -l '/\*\*' -- . ':!Documentation' ':!tools') \
+    | scripts/split-man.pl /tmp/man
+
+  $ scripts/kernel-doc -man \
+    $(git grep -l '/\*\*' -- . ":(exclude)Documentation" ":(exclude)tools") \
+    | scripts/split-man.pl /tmp/man