irqchip/stm32-exti: Map interrupts through interrupts-extended

The mapping of EXTI events to its parent interrupt controller is both SoC
and instance dependent.

The current implementation requires adding a new mapping table to the
driver's code and a new compatible for each new EXTI instance.

Check for the presence of the optional interrupts-extended property and use
it to map EXTI events to the parent's interrupts.

For old device trees without the optional interrupts-extended property, the
driver's behavior is unchanged, thus keeps backward compatibility.
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240415134926.1254428-4-antonio.borneo@foss.st.com

drivers/irqchip/irq-stm32-exti.c

@@ -61,6 +61,7 @@ struct stm32_exti_host_data {
 	struct stm32_exti_chip_data *chips_data;
 	const struct stm32_exti_drv_data *drv_data;
 	struct hwspinlock *hwlock;
+	bool dt_has_irqs_desc; /* skip internal desc_irqs array and get it from DT */
 };
 
 static struct stm32_exti_host_data *stm32_host_data;
@@ -731,6 +732,23 @@ static int stm32_exti_h_domain_alloc(struct irq_domain *dm,
 
 	irq_domain_set_hwirq_and_chip(dm, virq, hwirq, chip, chip_data);
 
+	if (host_data->dt_has_irqs_desc) {
+		struct of_phandle_args out_irq;
+		int ret;
+
+		ret = of_irq_parse_one(host_data->dev->of_node, hwirq, &out_irq);
+		if (ret)
+			return ret;
+		/* we only support one parent, so far */
+		if (of_node_to_fwnode(out_irq.np) != dm->parent->fwnode)
+			return -EINVAL;
+
+		of_phandle_args_to_fwspec(out_irq.np, out_irq.args,
+					  out_irq.args_count, &p_fwspec);
+
+		return irq_domain_alloc_irqs_parent(dm, virq, 1, &p_fwspec);
+	}
+
 	if (!host_data->drv_data->desc_irqs)
 		return -EINVAL;
 
@@ -975,6 +993,9 @@ static int stm32_exti_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	if (of_property_read_bool(np, "interrupts-extended"))
+		host_data->dt_has_irqs_desc = true;
+
 	stm32_exti_h_syscore_init(host_data);
 
 	return 0;