Intel/AMD x86 based computers now boot via a standard UEFI binary, which can load grub2, allows you to update the command line as needed, or select different version of the Linux kernel. On ARM everything is a little more complicated and messy, as bootloaders such as U-boot need to support different configurations formats.
Alexander Graf has been working on implementing UEFI support in U-boot, and it’s now supported by U-boot mainline and enabled by default for 32-bit and 64-bit ARM platforms, but not x86-64 (yet). That means you should now be able to boot any ARM boards supported by mainline U-boot through UEFI. Alexander gave a presentation about his work at an openSUSE event in June, and demonstrated u-boot with UEFI, and GRUB2 support with an openSUSE image running on a Raspberry Pi board.