dt-bindings: usb: mtu3: add wakeup interrupt

Add an dedicated interrupt which is usually EINT to support runtime PM,
meanwhile add "interrupt-names" property, for backward compatibility,
it's optional and used when wakeup interrupt exists

Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Chunfeng Yun <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/usb/mediatek,mtu3.yaml

···
       - const: ippc
 
   interrupts:
-    maxItems: 1
+    description:
+      use "interrupts-extended" when the interrupts are connected to the
+      separate interrupt controllers
+    minItems: 1
+    items:
+      - description: SSUSB device controller interrupt
+      - description: optional, wakeup interrupt used to support runtime PM
+
+  interrupt-names:
+    items:
+      - const: device
+      - const: wakeup
 
   power-domains:
     description: A phandle to USB power domain node to control USB's MTCMOS