dt-bindings: interrupt-controller: Document RZ/{T2H,N2H} ICU

dt-bindings: interrupt-controller: Document RZ/{T2H,N2H} ICU

The Renesas RZ/T2H (R9A09G077) and Renesas RZ/N2H (R9A09G087) SoCs have an
Interrupt Controller (ICU) block that routes external interrupts to the
GIC's SPIs, with the ability of level-translation, and can also produce
software interrupts and aggregate error interrupts.

It has 16 software triggered interrupts (INTCPUn), 16 external pin
interrupts (IRQn), a System error interrupt (SEI), two Cortex-A55 error
interrupts (CA55_ERRn), two Cortex-R52 error interrupts for each of the two
cores (CR52x_ERRn), two Peripheral error interrupts (PERI_ERRn), two DSMIF
error interrupts (DSMIF_ERRn), and two ENCIF error interrupts (ENCIF_ERRn).

The IRQn and SEI interrupts are exposed externally, while the others are
software triggered.

INTCPU0 to INTCPU13, IRQ 0 to IRQ13 are non-safety interrupts, while
INTCPU14, INTCPU15, IRQ14, IRQ15 and SEI are safety interrupts, and are
exposed via a separate register space.

Document them, and use RZ/T2H as a fallback for RZ/N2H as the ICU is
entirely compatible.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20251201112933.488801-2-cosmin-gabriel.tanislav.xa@renesas.com