How do I create a custom privilege

I want to create a custom privilege for my plugin and restrict the access to be plugin based on that privilege.

How do I create a custom privilege?

I came across - http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2004601

which suggests its doable but I can't find the API to get this done.

Please help.

Thanks in advance.

Regards,

Geeta