irqchip/gic-v2m: Use irq_domain_create_hierarchy()

Use the irq_domain_create_hierarchy() helper to create the hierarchical
domain, which both serves as documentation and avoids poking at
irqdomain internals.
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Hsin-Yi Wang <hsinyi@chromium.org>
Tested-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230213104302.17307-16-johan+linaro@kernel.org

drivers/irqchip/irq-gic-v2m.c

@@ -287,15 +287,14 @@ static __init int gicv2m_allocate_domains(struct irq_domain *parent)
 	if (!v2m)
 		return 0;
 
-	inner_domain = irq_domain_create_tree(v2m->fwnode,
-					      &gicv2m_domain_ops, v2m);
+	inner_domain = irq_domain_create_hierarchy(parent, 0, 0, v2m->fwnode,
+						   &gicv2m_domain_ops, v2m);
 	if (!inner_domain) {
 		pr_err("Failed to create GICv2m domain\n");
 		return -ENOMEM;
 	}
 
 	irq_domain_update_bus_token(inner_domain, DOMAIN_BUS_NEXUS);
-	inner_domain->parent = parent;
 	pci_domain = pci_msi_create_irq_domain(v2m->fwnode,
 					       &gicv2m_msi_domain_info,
 					       inner_domain);