how exactly does one standardize DeviceTree bindings?
The canonical repo is the Linux kernel tree, so you go through there (and the DeviceTree maintainers). This is mostly for practical reasons since they are the primary consumer, but the bindings are packaged for use by other OSes too.
(This is another difference between the Asahi Linux project and Corellium's kernel; we're going through the bureaucracy of standardizing all of our DeviceTree bindings, which takes time but establishes a common reference that other OSes such as OpenBSD and bootloaders such as U-Boot can use to also support drivers for this hardware using our first-level bootloader.)