spi: Stacked/parallel memories bindings

Merge series from Miquel Raynal <miquel.raynal@bootlin.com>:

DT bindings for stacked and parallel flash/memory devices.

base-commit: e783362e

Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml

@@ -47,7 +47,8 @@ properties:
       identified by the JEDEC READ ID opcode (0x9F).
 
   reg:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   spi-max-frequency: true
   spi-rx-bus-width: true

Documentation/devicetree/bindings/spi/spi-controller.yaml

@@ -139,4 +139,11 @@ examples:
             spi-max-frequency = <100000>;
             reg = <1>;
         };
+
+        flash@2 {
+          compatible = "jedec,spi-nor";
+          spi-max-frequency = <50000000>;
+          reg = <2>, <3>;
+          stacked-memories = /bits/ 64 <0x10000000 0x10000000>;
+        };
     };

Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml

@@ -83,6 +83,31 @@ properties:
     description:
       Delay, in microseconds, after a write transfer.
 
+  stacked-memories:
+    description: Several SPI memories can be wired in stacked mode.
+      This basically means that either a device features several chip
+      selects, or that different devices must be seen as a single
+      bigger chip. This basically doubles (or more) the total address
+      space with only a single additional wire, while still needing
+      to repeat the commands when crossing a chip boundary. The size of
+      each chip should be provided as members of the array.
+    $ref: /schemas/types.yaml#/definitions/uint64-array
+    minItems: 2
+    maxItems: 4
+
+  parallel-memories:
+    description: Several SPI memories can be wired in parallel mode.
+      The devices are physically on a different buses but will always
+      act synchronously as each data word is spread across the
+      different memories (eg. even bits are stored in one memory, odd
+      bits in the other). This basically doubles the address space and
+      the throughput while greatly complexifying the wiring because as
+      many busses as devices must be wired. The size of each chip should
+      be provided as members of the array.
+    $ref: /schemas/types.yaml#/definitions/uint64-array
+    minItems: 2
+    maxItems: 4
+
 # The controller specific properties go here.
 allOf:
   - $ref: cdns,qspi-nor-peripheral-props.yaml#