firmware: raspberrypi: Introduce rpi_firmware_find_node()

A significant number of RaspberryPi drivers using the firmware don't
have a phandle to it, so end up scanning the device tree to find a node
with the firmware compatible.

That code is duplicated everywhere, so let's introduce a helper instead.
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20220815-rpi-fix-4k-60-v5-1-fe9e7ac8b111@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/firmware/raspberrypi.c

@@ -311,6 +311,18 @@ static int rpi_firmware_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static const struct of_device_id rpi_firmware_of_match[] = {
+	{ .compatible = "raspberrypi,bcm2835-firmware", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, rpi_firmware_of_match);
+
+struct device_node *rpi_firmware_find_node(void)
+{
+	return of_find_matching_node(NULL, rpi_firmware_of_match);
+}
+EXPORT_SYMBOL_GPL(rpi_firmware_find_node);
+
 /**
  * rpi_firmware_get - Get pointer to rpi_firmware structure.
  * @firmware_node:    Pointer to the firmware Device Tree node.
@@ -366,12 +378,6 @@ struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(devm_rpi_firmware_get);
 
-static const struct of_device_id rpi_firmware_of_match[] = {
-	{ .compatible = "raspberrypi,bcm2835-firmware", },
-	{},
-};
-MODULE_DEVICE_TABLE(of, rpi_firmware_of_match);
-
 static struct platform_driver rpi_firmware_driver = {
 	.driver = {
 		.name = "raspberrypi-firmware",

include/soc/bcm2835/raspberrypi-firmware.h

@@ -142,6 +142,7 @@ int rpi_firmware_property(struct rpi_firmware *fw,
 int rpi_firmware_property_list(struct rpi_firmware *fw,
 			       void *data, size_t tag_size);
 void rpi_firmware_put(struct rpi_firmware *fw);
+struct device_node *rpi_firmware_find_node(void);
 struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node);
 struct rpi_firmware *devm_rpi_firmware_get(struct device *dev,
 					   struct device_node *firmware_node);
@@ -159,6 +160,12 @@ static inline int rpi_firmware_property_list(struct rpi_firmware *fw,
 }
 
 static inline void rpi_firmware_put(struct rpi_firmware *fw) { }
+
+static inline struct device_node *rpi_firmware_find_node(void)
+{
+	return NULL;
+}
+
 static inline struct rpi_firmware *rpi_firmware_get(struct device_node *firmware_node)
 {
 	return NULL;