GRUB is for a desktop PC architecture. No such thing on ARM embedded systems since they use a different bootloader (GRUB requires a system with a BIOS, embedded does not have a BIOS).
There is actually more to the story, but what you are interested in is the “
APPEND” key/value pair in “
/boot/extlinux/extlinux.conf”. Adding “
quiet splash pci=nomsi pcie_aspm=off” there would immediately cause the arguments to be passed to the kernel. There will actually be some inherited command line arguments as well, and those start in the device tree for earlier boot stages (prior to reaching the U-Boot bootloader), but you won’t need to mess with the device tree for those changes. If you were wanting to change behavior prior to the bootloader running, then you would need to deal with the device tree as well.