dt-bindings: mfd: max77620: Document optional RTC address for MAX77663

Document an optional second I2C address for the MAX77663 PMIC's RTC
device, to be used if the MAX77663 RTC is located at a non-default I2C
address.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260312085258.11431-5-clamor95@gmail.com
Signed-off-by: Lee Jones <lee@kernel.org>

Documentation/devicetree/bindings/mfd/maxim,max77620.yaml

@@ -17,7 +17,17 @@ properties:
       - maxim,max77663
 
   reg:
-    maxItems: 1
+    description:
+      Can contain an optional second I2C address pointing to the PMIC's
+      RTC device. If no RTC address is provided, a default address specific
+      to this PMIC will be used.
+    minItems: 1
+    maxItems: 2
+
+  reg-names:
+    items:
+      - const: pmic
+      - const: rtc
 
   interrupts:
     maxItems: 1
@@ -192,6 +202,16 @@ allOf:
                 maxim,suspend-fps-time-period-us:
                   enum: [40, 80, 160, 320, 640, 1280, 2560, 5120]
 
+  - if:
+      properties:
+        compatible:
+          not:
+            contains:
+              const: maxim,max77663
+    then:
+      properties:
+        reg-names: false
+
 required:
   - compatible
   - reg