I've now done a new footbridge patch, based a lot more closely on
Jason's work for xscale.

This seems to improve a few things, however it's still got a few issues,
even if minor:
- doing ftp seems to cause an underrun on the network card, I suspect
this is because we don't handle interrupts in priority order, and the
isa irq is 12, whereas my pci network card is on 18.  The fix is to
actually handle them in priority order, but that adds more overhead.
- isa interrupt handling still isn't great, I plan to improve it in a
seperate change.

I've tested this code, and it seems to work as well as the original
kernel, I can ftp, make things over nfs, play ogg files on usb speakers
etc.

The patch includes the relevant changes to netwinder as well as cats.

I've uploaded the patch and cats GENERIC kernel to:
ftp://ftp.netbsd.org/pub/NetBSD/arch/cats/newirq/
and a netwinder GENERIC kernel to:
ftp://ftp.netbsd.org/pub/NetBSD/arch/cats/newirq/netwinder/

If people can give them a try out, see how well they do.  I hope to
commit this week (possibly tommorrow, can also backout if it all goes
wrong, hmm, maybe I should branch this stuff so I can actually get it
all in place...)

Thanks,
Chris