dt-bindings: Document brcm, irq-can-wake for brcm, bcm7038-l1-intc.txt

The BCM7038 L1 interrupt controller can be used as a wake-up interrupt
controller on MIPS and ARM-based systems, document the brcm,irq-can-wake
which has been "standardized" across Broadcom interrupt controllers.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191024201415.23454-3-f.fainelli@gmail.com

Documentation/devicetree/bindings/interrupt-controller/brcm,bcm7038-l1-intc.txt

@@ -31,6 +31,11 @@ Required properties:
 - interrupts: specifies the interrupt line(s) in the interrupt-parent controller
   node; valid values depend on the type of parent interrupt controller
 
+Optional properties:
+
+- brcm,irq-can-wake: If present, this means the L1 controller can be used as a
+  wakeup source for system suspend/resume.
+
 If multiple reg ranges and interrupt-parent entries are present on an SMP
 system, the driver will allow IRQ SMP affinity to be set up through the
 /proc/irq/ interface.  In the simplest possible configuration, only one