custom kernel, debian source vs kernel.org source

In my process of building a custom kernel, I came across some problem appling the ACPI patches to the debian downloaded kernel source(2.4.20). I google around and found that the debian source is not a standard source tree but with its own patches applied. However, I was unable to find any information of how to patch a standard kernel source to the debian source. Is there any kernel expert here who can give me a hint or links for some information ?

check out

/usr/share/doc/kernel-source-2.4.20/README.Debian.gz

if you do: apt-get source kernel-source-2.4.20 you'll get diff that was applied to the official source.

apt-cache search kernel-patch will show you many patches that will apply nicely.

But I think your best bet would be to use this unofficial one (though I haven't tested it): http://people.debian.org/~baruch/deb/