dt-bindings: interrupt-controller: arm,gic-v3: Describe ESPI range support

GICv3.1 introduces support for new interrupt ranges, one of them being
the Extended SPI range (ESPI). The DT binding is extended to deal with
it as a new interrupt class.
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.yaml

@@ -44,11 +44,12 @@ properties:
       be at least 4.
 
       The 1st cell is the interrupt type; 0 for SPI interrupts, 1 for PPI
-      interrupts. Other values are reserved for future use.
+      interrupts, 2 for interrupts in the Extended SPI range. Other values
+      are reserved for future use.
 
       The 2nd cell contains the interrupt number for the interrupt type.
       SPI interrupts are in the range [0-987]. PPI interrupts are in the
-      range [0-15].
+      range [0-15]. Extented SPI interrupts are in the range [0-1023].
 
       The 3rd cell is the flags, encoded as follows:
       bits[3:0] trigger type and level flags.