Imho the most important part of the x86 standardization is the IBM pc platform. Arm boards doesn't have an equivalent platform to standardize on, so everybody does their own thing.
I find it unfortunate though that quite a few of the requirements for those standards is "buy more ARM IP blocks" rather than asking defining blocks that can be implemented by others.
There is the device tree[0], which Linux uses to know where all the ports are on an SoC. It’s become the de facto standard for ARM. Even non-Linux OSes like iOS adopted it.
Interestingly, Apple's use of device tree is older than even ARM's and Linux's. It was part of OpenFirmware and used in almost all of their Macs (and Mac derived lines like iOS) since the PowerMacs gained PCI slots. Even Intel Macs would use device tree internally too, for instance passing the user's password in the FDE unlock screen in the bootloader to the main OS via a DT chosen variable.
Unfortunately this is not common on ARM SBCs, at least not yet, they usually come with a SoC vendor supplied old kernel, and that's about it. And we forgive them, for the sake of low price.
Like Odroid Go Advance, a Rockchip 3326 based "retro handheld", and it's clones, was a tremendous hit of last year, still stuck with a 4.4 kernel.