gpiolib: Introduce for_each_gpiochip_node() loop helper

Introduce for_each_gpiochip_node() loop helper which iterates over
the GPIO controller child nodes of a given device.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>

include/linux/gpio/driver.h

@@ -3,13 +3,14 @@
 #define __LINUX_GPIO_DRIVER_H
 
 #include <linux/device.h>
-#include <linux/types.h>
 #include <linux/irq.h>
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdomain.h>
 #include <linux/lockdep.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinconf-generic.h>
+#include <linux/property.h>
+#include <linux/types.h>
 
 struct gpio_desc;
 struct of_phandle_args;
@@ -750,4 +751,8 @@ static inline void gpiochip_unlock_as_irq(struct gpio_chip *gc,
 }
 #endif /* CONFIG_GPIOLIB */
 
+#define for_each_gpiochip_node(dev, child)					\
+	device_for_each_child_node(dev, child)					\
+		if (!fwnode_property_present(child, "gpio-controller")) {} else
+
 #endif /* __LINUX_GPIO_DRIVER_H */