dts: gpio: add mention of pin number macros in nexus bindings docs

For all GPIO headers/connectors, add a short mention of the header file
that can be used to access pin numbers macros.

Signed-off-by: Benjamin Cabé <[email protected]>

Author: kartben

dts/bindings/gpio/arduino-mkr-header.yaml

@@ -33,6 +33,8 @@ description: |
         4  D4                   D7       7
         5  D5                   D6       6
 
+    Use ARDUINO_MKR_HEADER_* constants in <zephyr/dt-bindings/gpio/arduino-mkr-header.h> to refer to
+    specific pins using convenient constant names.
 
 compatible: "arduino-mkr-header"
 

dts/bindings/gpio/arduino-nano-header.yaml

@@ -32,6 +32,8 @@ description: |
         11 D11                  3V3    -
         12 D12                  D13    13
 
+    Use ARDUINO_NANO_HEADER_* constants in <zephyr/dt-bindings/gpio/arduino-nano-header.h>
+    to refer to specific pins using convenient constant names.
 
 compatible: "arduino-nano-header"
 

dts/bindings/gpio/raspberrypi,csi-connector.yaml

@@ -19,6 +19,9 @@ description: |
     3   I2C_SCL  pin 13 (15-pin based) / pin 20 (22-pin based)
     4   I2C_SDA  pin 14 (15-pin based) / pin 21 (22-pin based)
 
+  Use CSI_* constants in <zephyr/dt-bindings/gpio/raspberrypi-csi-connector.h>
+  to refer to specific pins using convenient constant names.
+
   For reference only, Raspberry 15-pin Connector layout:
     1   GND
     2   CSI_D0_N

dts/bindings/gpio/st-morpho-header.yaml

@@ -9,6 +9,9 @@ description: |
   any Nucleo board. They can be used to connect shields. All signals and power
   pins of the STM32 are available on the ST morpho connector.
 
+  Use ST_MORPHO_* constants in <zephyr/dt-bindings/gpio/st-morpho-header.h>
+  to refer to specific pins using convenient constant names.
+
 compatible: "st-morpho-header"
 
 include: [gpio-nexus.yaml, base.yaml]