Hm, just following the instructions doesn't work, because something or other's config.guess is too old. I guess lots of things need updating, which might make this a bit less trivial than I'd hoped...
If you are still interested in this: Building the rootfs for aarch64 seems to work pretty easy when using a current buildroot. I'm not sure about which kernel version to use though, I didn't find one in the repo where we get the other kernels from.
We (Linaro) have started looking at the image and, at first glance, it seems to be working. I'll post more details as we get them. Thank you for the work on this.
Hm, just following the instructions doesn't work, because something or other's config.guess is too old. I guess lots of things need updating, which might make this a bit less trivial than I'd hoped...