irqchip/gic-v3: Make gic_irq_domain_select() robust for zero parameter count

Currently the irqdomain select callback is only invoked when the parameter
count of the fwspec arguments is not zero. That makes sense because then
the match is on the firmware node and eventually on the bus_token, which is
already handled in the core code.

The upcoming support for per device MSI domains requires to do real bus
token specific checks in the MSI parent domains with a zero parameter
count.

Make the gic-v3 select() callback handle that case.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240127161753.114685-2-apatel@ventanamicro.com

drivers/irqchip/irq-gic-v3.c

@@ -1702,9 +1702,13 @@ static int gic_irq_domain_select(struct irq_domain *d,
 	irq_hw_number_t hwirq;
 
 	/* Not for us */
-        if (fwspec->fwnode != d->fwnode)
+	if (fwspec->fwnode != d->fwnode)
 		return 0;
 
+	/* Handle pure domain searches */
+	if (!fwspec->param_count)
+		return d->bus_token == bus_token;
+
 	/* If this is not DT, then we have a single domain */
 	if (!is_of_node(fwspec->fwnode))
 		return 1;