Add tip on switching git tag

source/clear-linux/guides/maintenance/kernel-development.rst

@@ -80,8 +80,16 @@ Clone the existing kernel package repository from |CL| as a starting point.
     You can alternatively use a different kernel variant as the base for modification. 
     For a list of kernel package names which you can clone instead, see the `clearlinux-pkgs GitHub`_.
 
+    The latest version of the |CL| kernel package is pulled as a starting 
+    point. An older version can pulled by switching to different git tag with 
+    :command:`git checkout tag/${TAG_NAME}` tag.
 
 
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 Change the kernel version 
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