dt-bindings: soundwire: qcom: document optional wake irq

Wake IRQ is optional interrupt that can be wired up on SoundWire controller
instances like RX path along with MBHC(Multi Button Headset connection).
Document this in bindings.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20220228172528.3489-3-srinivas.kandagatla@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: Srinivas-Kandagatla

Documentation/devicetree/bindings/soundwire/qcom,sdw.txt

@@ -22,7 +22,19 @@ board specific bus parameters.
 - interrupts:
 	Usage: required
 	Value type: <prop-encoded-array>
-	Definition: should specify the SoundWire Controller IRQ
+	Definition: should specify the SoundWire Controller core and optional
+		    wake IRQ
+
+- interrupt-names:
+	Usage: Optional
+	Value type: boolean
+	Value type: <stringlist>
+	Definition: should be "core" for core and "wakeup" for wake interrupt.
+
+- wakeup-source:
+	Usage: Optional
+	Value type: boolean
+	Definition: should specify if SoundWire Controller is wake up capable.
 
 - clock-names:
 	Usage: required