OrangePi Zero Plus enable uart3

[nottledim]

The OrangePi Zero Plus is a Allwinner H5 based 64bit SBC. It works well with ArchLinuxArm aarch64.

However I'm totally perplexed as to how to enable the uarts and other devices. There seems to be no mechanism for doing dt overlays or whatever is needed to enable these things.

I have managed to enable devices on an OrangePi One by copying bits of u-boot boot.cmd and overlay files from Armbian. But there must be a better way.

Is there any documentation explaining how to update device tree in ArchLinuxArm?