dt-bindings: virtio: mmio: add optional wakeup-source property

Some systems want to set the interrupt of virtio_mmio device
as a wakeup source. On such systems, we'll use the existence
of the "wakeup-source" property as a signal of requirement.

Signed-off-by: Minghao Xue <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

Documentation/devicetree/bindings/virtio/mmio.yaml

···
     description: Required for devices making accesses thru an IOMMU.
     maxItems: 1
 
+  wakeup-source:
+    type: boolean
+    description: Required for setting irq of a virtio_mmio device as wakeup source.
+
 required:
   - compatible
   - reg