dts: arm: rpi_pico: remove #define from dts

Removing direct #define usage in the DTSI file and converting these
definitions to use a dt-bindings header instead.

Relocates the RPI_PICO_DEFAULT_IRQ_PRIORITY definition to a DTSI file and
introduces an override.dtsi file. The override file is used when no other
override file is present, allowing for better flexibility and compliance
with Zephyr’s DTS structure.

Fixes: #79719

Signed-off-by: Tarang Raval <tarang.raval@siliconsignals.io>

dts/arm/rpi_pico/override.dtsi

@@ -0,0 +1,7 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ */
+/*
+ * File intentionally left blank. Will be used when there is no other
+ * higher-priority override.dtsi file in use.
+ */

dts/arm/rpi_pico/rp2040.dtsi

@@ -10,9 +10,17 @@
 #include <zephyr/dt-bindings/clock/rpi_pico_clock.h>
 #include <zephyr/dt-bindings/i2c/i2c.h>
 #include <zephyr/dt-bindings/regulator/rpi_pico.h>
+#include <zephyr/dt-bindings/reset/rpi_pico_reset.h>
 #include <mem.h>
 
-#include "rpi_pico_common.dtsi"
+#include <arm/rpi_pico/override.dtsi>
+/*
+ * This value can be overridden at the board level or in an application specific
+ * override.dtsi file.
+ */
+#ifndef RPI_PICO_DEFAULT_IRQ_PRIORITY
+#define RPI_PICO_DEFAULT_IRQ_PRIORITY 3
+#endif
 
 / {
 	aliases {

include/zephyr/dt-bindings/reset/rpi_pico_reset.h

@@ -4,10 +4,6 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-#ifndef RPI_PICO_DEFAULT_IRQ_PRIORITY
-#define RPI_PICO_DEFAULT_IRQ_PRIORITY 3
-#endif
-
 #define RPI_PICO_RESETS_RESET_ADC		0
 #define RPI_PICO_RESETS_RESET_BUSCTRL		1
 #define RPI_PICO_RESETS_RESET_DMA		2