Things required to "support" Pi3 aarch64 that aren't already in place in core CentOS (or at least I haven't managed to find them):
1) Pi3 firmware blobs
Trivially downloadable from
2) UEFI bootloader
There are two options, u-boot and Tianocore.
My current Pi3 aarch64 image works with u-boot that I grabbed from the Fedora 26 image.
I'm currently trying to get it working with Tianocore from here:
I _almost_ have it working (gets as far as booting grub, but grub then doesn't manage to boot up the kernel, almost certainly a dtb issue somewhere).
3) Kernel
I keep my own mainline kernel build for aarch64, loosely based on, IIRC, 4.5.x that shipped with CentOS aarch64, but with some modifications. I have a build that works on both my X-Gene and the Pi3. You can find it here:
(Note: I only included Pi 3 SoC configuration as of 4.9.73).
So it's not exactly an insurmountable problem, it's just a case off dropping a tarball of 5-6 files onto the /boot/efi FAT partition, having the appropriate kernel installed in the image, and it should "just work".
I can have a working image with u-boot EFI as soon as I find half an hour to spare.
The one with Tianocore EFI will take a little longer.