dt-bindings: samsung: exynos-pmu: Narrow allowed reboot modes

syscon-reboot-mode schema allows arbitrary "mode-.* properties but only
a subset actually makes sense and is valid.  Provide negative look-ahead
pattern to disallow any modes not supported by the device, which
tightens the binding.

Most of Android-based Exynos devices share the bootloader or its parts,
thus reboot modes are most likely the same, however only a few upstream
DTS define them, so add restrictions only for these.

Google GS101 has on the other hand quite different bootloader with many
known reboot modes.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260701105731.196618-4-krzysztof.kozlowski@oss.qualcomm.com
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml

@@ -176,6 +176,20 @@ allOf:
       properties:
         dp-phy: false
 
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - samsung,exynos7-pmu
+    then:
+      properties:
+        reboot-mode:
+          patternProperties:
+            # Negative look-ahead to disallow unsupported modes. The '$' has to be
+            # part of lookahead group to work, instead of trailing outside of ().
+            "^mode-(?!(bootloader$|download$|fastboot$|recovery$))": false
+
   - if:
       properties:
         compatible:
@@ -183,6 +197,13 @@ allOf:
             enum:
               - google,gs101-pmu
     then:
+      properties:
+        reboot-mode:
+          patternProperties:
+            # Negative look-ahead to disallow unsupported modes. The '$' has to be
+            # part of lookahead group to work, instead of trailing outside of ().
+            "^mode-(?!(bootloader$|charge$|dm-verity-device-corrupted$|fastboot$|reboot-ab-update$|recovery$)|rescue$|shutdown-thermal$|shutdown-thermal-battery$)": false
+
       required:
         - google,pmu-intr-gen-syscon
     else: