regulator: dt-bindings: fixed-regulator: Add under-voltage interrupt support

Add under-voltage interrupt support. This can be used with simple
regulators having no other way to communicate an under-voltage event
except as by toggling some GPIO line.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Link: https://lore.kernel.org/r/20231025084614.3092295-4-o.rempel@pengutronix.deSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/fixed-regulator.yaml

@@ -100,6 +100,11 @@ properties:
   vin-supply:
     description: Input supply phandle.
 
+  interrupts:
+    maxItems: 1
+    description:
+      Interrupt signaling a critical under-voltage event.
+
 required:
   - compatible
   - regulator-name