Add a description of the External Interrupt Unit (EXIU) interrupt
controller as found on the Socionext SynQuacer SoC.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>