dt-bindings: iio: adc: adi,ad7{124,173,192,780}: Allow specifications of a gpio for irq line

For the AD7124 chip and some of its cousins the logical irq line (R̅D̅Y̅)
is physically on the same pin as the spi MISO output (DOUT) and so
reading a register might trigger an interrupt. For correct operation
it's critical that the actual state of the pin can be read to judge if
an interrupt event is a real one or just a spurious one triggered by
toggling the line in its MISO mode.

Allow specification of an "rdy-gpios" property that references a GPIO
that can be used for that purpose. While this is typically the same GPIO
also used (implicitly) as interrupt source, it is still supposed that
the interrupt is specified as before and usual.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://patch.msgid.link/7fc92a8539e55802d514332e70ee836a3ed08b66.1733504533.git.u.kleine-koenig@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/devicetree/bindings/iio/adc/adi,ad7124.yaml

@@ -37,6 +37,17 @@ properties:
     description: IRQ line for the ADC
     maxItems: 1
 
+  rdy-gpios:
+    description:
+      GPIO reading the R̅D̅Y̅ line. Having such a GPIO is technically optional but
+      highly recommended because DOUT/R̅D̅Y̅ toggles during SPI transfers (in its
+      DOUT aka MISO role) and so usually triggers a spurious interrupt. The
+      distinction between such a spurious event and a real one can only be done
+      by reading such a GPIO. (There is a register telling the same
+      information, but accessing that one needs a SPI transfer which then
+      triggers another interrupt event.)
+    maxItems: 1
+
   '#address-cells':
     const: 1
 
@@ -111,6 +122,7 @@ unevaluatedProperties: false
 
 examples:
   - |
+    #include <dt-bindings/gpio/gpio.h>
     spi {
       #address-cells = <1>;
       #size-cells = <0>;
@@ -121,6 +133,7 @@ examples:
         spi-max-frequency = <5000000>;
         interrupts = <25 2>;
         interrupt-parent = <&gpio>;
+        rdy-gpios = <&gpio 25 GPIO_ACTIVE_LOW>;
         refin1-supply = <&adc_vref>;
         clocks = <&ad7124_mclk>;
         clock-names = "mclk";

Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml

@@ -135,6 +135,17 @@ properties:
   '#clock-cells':
     const: 0
 
+  rdy-gpios:
+    description:
+      GPIO reading the R̅D̅Y̅ line. Having such a GPIO is technically optional but
+      highly recommended because DOUT/R̅D̅Y̅ toggles during SPI transfers (in its
+      DOUT aka MISO role) and so usually triggers a spurious interrupt. The
+      distinction between such a spurious event and a real one can only be done
+      by reading such a GPIO. (There is a register telling the same
+      information, but accessing that one needs a SPI transfer which then
+      triggers another interrupt event.)
+    maxItems: 1
+
 patternProperties:
   "^channel@[0-9a-f]$":
     type: object
@@ -443,6 +454,7 @@ examples:
         interrupts = <25 IRQ_TYPE_EDGE_FALLING>;
         interrupt-names = "rdy";
         interrupt-parent = <&gpio>;
+        rdy-gpios = <&gpio 25 GPIO_ACTIVE_LOW>;
         spi-max-frequency = <5000000>;
         gpio-controller;
         #gpio-cells = <2>;

Documentation/devicetree/bindings/iio/adc/adi,ad7192.yaml

@@ -106,6 +106,17 @@ properties:
     description: see Documentation/devicetree/bindings/iio/adc/adc.yaml
     type: boolean
 
+  rdy-gpios:
+    description:
+      GPIO reading the R̅D̅Y̅ line. Having such a GPIO is technically optional but
+      highly recommended because DOUT/R̅D̅Y̅ toggles during SPI transfers (in its
+      DOUT aka MISO role) and so usually triggers a spurious interrupt. The
+      distinction between such a spurious event and a real one can only be done
+      by reading such a GPIO. (There is a register telling the same
+      information, but accessing that one needs a SPI transfer which then
+      triggers another interrupt event.)
+    maxItems: 1
+
 patternProperties:
   "^channel@[0-9a-f]+$":
     type: object
@@ -181,6 +192,7 @@ unevaluatedProperties: false
 
 examples:
   - |
+    #include <dt-bindings/gpio/gpio.h>
     spi {
         #address-cells = <1>;
         #size-cells = <0>;
@@ -195,6 +207,7 @@ examples:
             clock-names = "mclk";
             interrupts = <25 0x2>;
             interrupt-parent = <&gpio>;
+            rdy-gpios = <&gpio 25 GPIO_ACTIVE_LOW>;
             aincom-supply = <&aincom>;
             dvdd-supply = <&dvdd>;
             avdd-supply = <&avdd>;
@@ -207,6 +220,7 @@ examples:
         };
     };
   - |
+    #include <dt-bindings/gpio/gpio.h>
     spi {
         #address-cells = <1>;
         #size-cells = <0>;
@@ -224,6 +238,7 @@ examples:
             #clock-cells = <0>;
             interrupts = <25 0x2>;
             interrupt-parent = <&gpio>;
+            rdy-gpios = <&gpio 25 GPIO_ACTIVE_LOW>;
             aincom-supply = <&aincom>;
             dvdd-supply = <&dvdd>;
             avdd-supply = <&avdd>;

Documentation/devicetree/bindings/iio/adc/adi,ad7780.yaml

@@ -63,6 +63,17 @@ properties:
       marked GPIO_ACTIVE_LOW.
     maxItems: 1
 
+  rdy-gpios:
+    description:
+      GPIO reading the R̅D̅Y̅ line. Having such a GPIO is technically optional but
+      highly recommended because DOUT/R̅D̅Y̅ toggles during SPI transfers (in its
+      DOUT aka MISO role) and so usually triggers a spurious interrupt. The
+      distinction between such a spurious event and a real one can only be done
+      by reading such a GPIO. (There is a register telling the same
+      information, but accessing that one needs a SPI transfer which then
+      triggers another interrupt event.)
+    maxItems: 1
+
 required:
   - compatible
   - reg