[PATCH v1 08/13] dt-bindings: iio: adc: adi,ad4134: Document SPI connection mode

[Marcelo Schmitt <marcelo.schmitt@analog.com>]

Document how AD4134 chips are connected to the host SPI controller
according to different wiring configurations.

Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
---
 .../bindings/iio/adc/adi,ad4134.yaml          | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
index ea6d7e026419..d843c02a394a 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
@@ -131,6 +131,28 @@ properties:
     enum: [ free-running, gated ]
     default: gated
 
+  adi,spi-mode:
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ no-cs, 4-wire, one-channel-chain, two-channel-chain ]
+    description: |
+      This property indicates the SPI wiring configuration.
+
+      When this property is omitted, it is assumed that the device is using
+      'no-cs' wiring. When this property is present, it indicates that the
+      device is using one of the following wiring configurations:
+
+      * no-cs: The datasheet calls this "minimum I/O mode". In this mode, the CS
+        line is not used (tied to GND).
+      * 4-wire: Specifies a conventional SPI wiring configuration.
+      * one-channel-chain: In this mode, the DOUT0 line of one chip is connected
+        to DOUT2 of the next chip upstream in the chain. Only the data interface
+        of the upmost device in the stream is in direct connection with the
+        digital host.
+      * two-channel-chain: In this mode, the DOUT0 and DOUT1 lines of one chip
+        are respectively connected to DOUT2 and DOUT3 of the next chip upstream
+        in the chain. Only the data interface of the upmost device in the stream
+        is in direct connection with the digital host.
+
 required:
   - compatible
   - reg
-- 
2.53.0