[PATCH v3 2/3] spi: dt-bindings: Describe stacked/parallel memories modes

[Miquel Raynal]

Describe two new memories modes:
- A stacked mode when the bus is common but the address space extended
  with an additinals wires.
- A parallel mode with parallel busses accessing parallel flashes where
  the data is spread.

Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
---
 .../bindings/spi/spi-peripheral-props.yaml    | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
index 5dd209206e88..13aa6a2374c9 100644
--- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
+++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
@@ -82,6 +82,27 @@ properties:
     description:
       Delay, in microseconds, after a write transfer.
 
+  stacked-memories:
+    type: boolean
+    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. XIP is
+      usually not supported in this mode.
+
+  parallel-memories:
+    type: boolean
+    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. XIP is usually not
+      supported in this mode.
+
 # The controller specific properties go here.
 allOf:
   - $ref: cdns,qspi-nor-peripheral-props.yaml#
-- 
2.27.0