Add empty weak assembler function armv8_switch_to_el2_prep() which is
jumped to just before U-Boot determines which EL it is running in and
decides which path to take to boot the Linux kernel.
This weak function is meant to be used by architecture specific code
to implement jump to a firmware blob, which then returns right past
this weak function and continues execution of U-Boot code which then
boots the Linux kernel. One example of such use case is when U-Boot
jump tp TFA BL31, which switches from EL3 to EL2 and then returns to
U-Boot code newly running in EL2 and starts the Linux kernel.
The weak function is called with caches already disabled and DM shut
down. Any preparatory work or even loading of more data must be done
in board_prep_linux(), this hook is meant only for the final jump to
the firmware and return to U-Boot before booting Linux.
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
9f95282f31