dt-bindings: memory: tegra124: emc: Document OPP table and voltage regulator

Document new OPP table and voltage regulator properties which are needed
for supporting dynamic voltage-frequency scaling of the memory controller.
Some boards may have a fixed core voltage regulator, hence it's optional
because frequency scaling still may be desired.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201104164923.21238-15-digetx@gmail.comSigned-off-by: Krzysztof Kozlowski <krzk@kernel.org>

Documentation/devicetree/bindings/memory-controllers/nvidia,tegra124-emc.yaml

@@ -37,6 +37,15 @@ properties:
     description:
       phandle of the memory controller node
 
+  core-supply:
+    description:
+      Phandle of voltage regulator of the SoC "core" power domain.
+
+  operating-points-v2:
+    description:
+      Should contain freqs and voltages and opp-supported-hw property, which
+      is a bitfield indicating SoC speedo ID mask.
+
 patternProperties:
   "^emc-timings-[0-9]+$":
     type: object
@@ -331,6 +340,7 @@ required:
   - clock-names
   - nvidia,memory-controller
   - "#interconnect-cells"
+  - operating-points-v2
 
 additionalProperties: false
 
@@ -359,6 +369,8 @@ examples:
         clock-names = "emc";
 
         nvidia,memory-controller = <&mc>;
+        operating-points-v2 = <&dvfs_opp_table>;
+        core-supply = <&vdd_core>;
 
         #interconnect-cells = <0>;