dt-bindings: interrupt-controller: realtek,rtl-intc: require parents

dt-bindings: interrupt-controller: realtek,rtl-intc: require parents

The interrupt router has 32 inputs, and up to 15 outputs connected to
the MIPS CPU's interrupts. The way these are mapped to each other is
runtime configurable. This controller can also mask individual interrupt
sources, and has a status register to indicate pending interrupts. This
means the controller is not transparent, and the use of "interrupt-map"
inappropriate. Instead, a list of parent interrupts should be specified.

Two-part compatibles are introduced to be able to require "interrupts"
for new devicetrees. For backward compatibility "interrupt-map" is still
allowed on these new compatibles, but deprecated. The old compatible,
with required "interrupt-map" and "#address-cells", is also deprecated.
The relevant descriptions are added or extended to more clearly describe
the functionality of this controller.

To prevent spurious changes to the binding when more SoCs are added,
"allOf" is used with one "if", and the compatible enum only has one
item.

The example is updated to provide a correct example for RTL8380 SoCs.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/ba3ae8e521ef82dd94f18a602ef53078f4a0d8d5.1663617425.git.sander@svanheule.net