irqchip/meson-gpio: Make it possible to build as a module

In order to reduce the kernel Image size on multi-platform distributions,
make it possible to build the Amlogic GPIO IRQ controller as a module
by switching it to a platform driver.

Signed-off-by: Neil Armstrong <[e-mail]>
Acked-by: Saravana Kannan <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Reviewed-by: Lee Jones <[e-mail]>
Reviewed-by: Kevin Hilman <[e-mail]>
Tested-by: Kevin Hilman <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/irqchip/Kconfig

···
 	  Support for the UniPhier AIDET (ARM Interrupt Detector).
 
 config MESON_IRQ_GPIO
-       bool "Meson GPIO Interrupt Multiplexer"
-       depends on ARCH_MESON
+       tristate "Meson GPIO Interrupt Multiplexer"
+       depends on ARCH_MESON || COMPILE_TEST
+       default ARCH_MESON
        select IRQ_DOMAIN_HIERARCHY
        help
          Support Meson SoC Family GPIO Interrupt Multiplexer

drivers/irqchip/irq-meson-gpio.c

···
 	.translate	= meson_gpio_irq_domain_translate,
 };
 
-static int __init meson_gpio_irq_parse_dt(struct device_node *node,
-					  struct meson_gpio_irq_controller *ctl)
+static int meson_gpio_irq_parse_dt(struct device_node *node, struct meson_gpio_irq_controller *ctl)
 {
 	const struct of_device_id *match;
 	int ret;
···
 	return 0;
 }
 
-static int __init meson_gpio_irq_of_init(struct device_node *node,
-					 struct device_node *parent)
+static int meson_gpio_irq_of_init(struct device_node *node, struct device_node *parent)
 {
 	struct irq_domain *domain, *parent_domain;
 	struct meson_gpio_irq_controller *ctl;
···
 	return ret;
 }
 
-IRQCHIP_DECLARE(meson_gpio_intc, "amlogic,meson-gpio-intc",
-		meson_gpio_irq_of_init);
+IRQCHIP_PLATFORM_DRIVER_BEGIN(meson_gpio_intc)
+IRQCHIP_MATCH("amlogic,meson-gpio-intc", meson_gpio_irq_of_init)
+IRQCHIP_PLATFORM_DRIVER_END(meson_gpio_intc)
+
+MODULE_AUTHOR("Jerome Brunet <[e-mail]>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:meson-gpio-intc");