Just to add: a stable identifier for platform resources is platform knowledge, hence always handed down from bootloader to linux. Multiple mechanisms for this exist (DT, ACPI) and aren't going to go away, so a "linux generic" solution isn't possible.

Meanwhile the of_alias mechanism is simple and generic across all architectures that use DT, and is already in use by multiple subsystems. Its main flaw is being poorly documented, like so many kernel-things.

Anyway, hns wanted to know why this isn't upstream or being upstreamed, I think I've informed all parties as well as I can about this. I would still appreciate it being applied at least while we're doing mmc testing since it reduces the risk of confusion. I intend to keep it indefinitely in kernels I build personally. I don't intend to spend more time and energy on this discussion.