dt-bindings: mmc: cdns: Add AMD Pensando Elba SoC

AMD Pensando Elba ARM 64-bit SoC is integrated with this IP and
explicitly controls byte-lane enables.

Signed-off-by: Brad Larson <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

Documentation/devicetree/bindings/mmc/cdns,sdhci.yaml

···
 maintainers:
   - Masahiro Yamada <[e-mail]>
 
-allOf:
-  - $ref: mmc-controller.yaml
-
 properties:
   compatible:
     items:
       - enum:
+          - amd,pensando-elba-sd4hc
           - microchip,mpfs-sd4hc
           - socionext,uniphier-sd4hc
       - const: cdns,sd4hc
 
   reg:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   interrupts:
     maxItems: 1
···
   - reg
   - interrupts
   - clocks
+
+allOf:
+  - $ref: mmc-controller.yaml
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: amd,pensando-elba-sd4hc
+    then:
+      properties:
+        reg:
+          items:
+            - description: Host controller registers
+            - description: Elba byte-lane enable register for writes
+      required:
+        - resets
+    else:
+      properties:
+        reg:
+          maxItems: 1
 
 unevaluatedProperties: false