Correct way to enable port multiplier support in kernel 2.6.20-1?

I don't see any patches to get port multiplier support working for kernel 2.6.20-1 I recompiled the kernel manually and made sure I config'd it with everything current but it appears port multiplier isn't in the mainline (it still does not work). My question is, what do I need to do to get my addonics 3726 working with kernel 2.6.20-1? I'm not a developer by any means and the guide on the addonics website would have worked for me but it is out of date.
http://www.addonics.com/support/faqs/faq-pmsupport_desktop.asp

Gene Stapp