If they want to compete they have to agree on something like ACPI so the OS vendors can target their boards without a separate distribution for each board.
Most ARM boards already use Device Tree with Linux, there isn't any new agreement needed. What is missing is getting the drivers for each board into the same source tree.
NetBSD provides a filesystem image containing one kernel that will boot on all supported ARMv8 boards, you may need to write a board-specific build of u-boot to the start of that image. A Linux distribution could do the same as this.
NetBSD provides a filesystem image containing one kernel that will boot on all supported ARMv8 boards, you may need to write a board-specific build of u-boot to the start of that image. A Linux distribution could do the same as this.