This patch adds a rudimentary header file with defines for FF-A ABIs that will be used as the transport between S-EL0 and the SPM Signed-off-by: Achin Gupta <achin.gupta@arm.com> Reviewed-by: Sami Mujawar <sami.mujawar@arm.com> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>