I'm using the 2.4.x-xxx-yyy-zzz-ads1 source tree. You just released a 2.4.x-xxx-yyy-zzz-ads2 patch. Can I apply the ads2 patch over the ads1 source tree?
Unfortunately, no. You must make a new source tree starting with the 2.4.x kernel and then apply each maintainer's patch, in order. Linux patches always start from original patch. That means, for example that if you have a 2.4.1-rmk1-np1 source tree and there is a new np2 patch for 2.4.1-rmk1, then you should make a source tree from the 2.4.1 kernel, apply the rmk1 patch, and then the np2 patch.