Hi Mike,
I've also had a go at patching the kernel for the newer VIA southbridge support. However, I did not use the patch file from LWN as, like you, I found that the patch failed at every hunk. I used the patch from VIA themselves. It only fails at 2 places (out of quite a few) and I manually examined and patched the required lines of the corresponding source files. The VIA patch was meant for the oiriginal RH 7.3 kernel source and not the updated kernel used by SME 5.6.
Unfortunately, I still cannot recompile the kernel using the DevTools packages from contribs.org as the compile process generates errors about invalid / missing paths, files, etc. I've used the DevTools packages to compile other things like drivers, etc. before without a hitch as they did not involve the affected kernel headers or source files. As I did not want to mess with the kernel sources too much in case I really broke something, I gave up on it (it was also getting tedious - more urgent things to do). However, if someone with more time and experience managed to get the new kernel going, it would be much appreciated as I have had first hand experience of things going badly wrong if you proceed to use SME 5.6 on the motherboards with these chipsets (poor performance, data corruption, IDE tape drive that won't work reliably, etc). I actually have one such m/b in a production environment but it is using an add-in controller to drive the hdds and other bits therefore the southbridge problem did not directly affect this particular system.
Kelvin