From 86ddc446fd7936fdc1ad5a79a8fe1fd9f30ca3f6 Mon Sep 17 00:00:00 2001
From: Markus Stockhausen <markus.stockhausen@gmx.de>
Date: Fri, 5 Jun 2026 23:16:44 +0200
Subject: [PATCH] irqchip/irq-realtek-rtl: Add a select function

When working with multiple domains, the interrupt registration
must know to which domain it attaches. Add a select function that
takes care of the lookup. Logic is as follows.

If a device needs explicit parent routing it can request it by
giving an index as a second argument in the device tree. E.g.

intc: interrupt-controller@3000 {
  ...
  interrupts = <2>, <3>, <4>, <5>, <6>, <7>;
};

uart1: uart@2100 {
  ...
  interrupt-parent = <&intc>;
  interrupts = <31 1>;
}

This way the serial console with hardware interrupt 31 will be
routed via SoC interrupt 3. If the second argument is not given,
the first parent interrupt of the controller is selected.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260605211646.2101652-6-markus.stockhausen@gmx.de
---
 drivers/irqchip/irq-realtek-rtl.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-realtek-rtl.c b/drivers/irqchip/irq-realtek-rtl.c
index 9f792d4cb503..b256f9803fd7 100644
--- a/drivers/irqchip/irq-realtek-rtl.c
+++ b/drivers/irqchip/irq-realtek-rtl.c
@@ -26,7 +26,9 @@
 #define REG(cpu, x)		(realtek_ictl_base[cpu] + x)
 
 struct realtek_ictl_output {
+	struct fwnode_handle	*fwnode;
 	struct irq_domain	*domain;
+	unsigned int		index;
 	u32			mask;
 };
 
@@ -125,9 +127,25 @@ static int intc_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hw_i
 	return 0;
 }
 
+static int intc_select(struct irq_domain *d, struct irq_fwspec *fwspec,
+		       enum irq_domain_bus_token bus_token)
+{
+	struct realtek_ictl_output *output = d->host_data;
+	unsigned int index = 0;
+
+	if (fwspec->fwnode != output->fwnode)
+		return false;
+
+	if (fwspec->param_count == 2)
+		index = fwspec->param[1];
+
+	return index == output->index;
+}
+
 static const struct irq_domain_ops irq_domain_ops = {
-	.map = intc_map,
-	.xlate = irq_domain_xlate_onecell,
+	.map	= intc_map,
+	.select	= intc_select,
+	.xlate	= irq_domain_xlate_onecell,
 };
 
 static void realtek_irq_dispatch(struct irq_desc *desc)
@@ -197,6 +215,8 @@ static int __init realtek_setup_parents(struct device_node *node)
 	}
 
 	output->domain = domain;
+	output->fwnode = of_fwnode_handle(node);
+	output->index = 0;
 	irq_set_chained_handler_and_data(parent_irq, realtek_irq_dispatch, output);
 
 	return 0;