dt-bindings: interrupt-controller: mpm: Pass MSG RAM slice through phandle

Due to the wild nature of the Qualcomm RPM Message RAM, the kernel can't
really use 'reg' to point to the MPM's slice of Message RAM without cutting
into an already-defined RPM MSG RAM node used for GLINK and SMEM.

Document passing the register space as a slice of SRAM through the
qcom,rpm-msg-ram property. This also makes 'reg' deprecated.
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230328-topic-msgram_mpm-v7-1-6ee2bfeaac2c@linaro.org

Documentation/devicetree/bindings/interrupt-controller/qcom,mpm.yaml

@@ -29,6 +29,12 @@ properties:
     maxItems: 1
     description:
       Specifies the base address and size of vMPM registers in RPM MSG RAM.
+    deprecated: true
+
+  qcom,rpm-msg-ram:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to the APSS MPM slice of the RPM Message RAM
 
   interrupts:
     maxItems: 1
@@ -64,23 +70,35 @@ properties:
 
 required:
   - compatible
-  - reg
   - interrupts
   - mboxes
   - interrupt-controller
   - '#interrupt-cells'
   - qcom,mpm-pin-count
   - qcom,mpm-pin-map
+  - qcom,rpm-msg-ram
 
 additionalProperties: false
 
 examples:
   - |
     #include <dt-bindings/interrupt-controller/arm-gic.h>
-    mpm: interrupt-controller@45f01b8 {
+
+    remoteproc-rpm {
+        compatible = "qcom,msm8998-rpm-proc", "qcom,rpm-proc";
+
+        glink-edge {
+            compatible = "qcom,glink-rpm";
+
+            interrupts = <GIC_SPI 168 IRQ_TYPE_EDGE_RISING>;
+            qcom,rpm-msg-ram = <&rpm_msg_ram>;
+            mboxes = <&apcs_glb 0>;
+        };
+
+        mpm: interrupt-controller {
             compatible = "qcom,mpm";
+            qcom,rpm-msg-ram = <&apss_mpm>;
             interrupts = <GIC_SPI 197 IRQ_TYPE_EDGE_RISING>;
-        reg = <0x45f01b8 0x1000>;
             mboxes = <&apcs_glb 1>;
             interrupt-controller;
             #interrupt-cells = <2>;
@@ -91,6 +109,6 @@ examples:
                                <12 422>,
                                <24 79>,
                                <86 183>,
-                           <90 260>,
                                <91 260>;
         };
+    };