irqchip/gic-v3-its: 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.

Note that the domain host_data was first set to the struct its_node
during allocation only to immediately be overwritten with the struct
msi_domain_info.
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/20230213104302.17307-17-johan+linaro@kernel.org

drivers/irqchip/irq-gic-v3-its.c

@@ -4909,18 +4909,19 @@ static int its_init_domain(struct fwnode_handle *handle, struct its_node *its)
 	if (!info)
 		return -ENOMEM;
 
-	inner_domain = irq_domain_create_tree(handle, &its_domain_ops, its);
+	info->ops = &its_msi_domain_ops;
+	info->data = its;
+
+	inner_domain = irq_domain_create_hierarchy(its_parent,
+						   its->msi_domain_flags, 0,
+						   handle, &its_domain_ops,
+						   info);
 	if (!inner_domain) {
 		kfree(info);
 		return -ENOMEM;
 	}
 
-	inner_domain->parent = its_parent;
 	irq_domain_update_bus_token(inner_domain, DOMAIN_BUS_NEXUS);
-	inner_domain->flags |= its->msi_domain_flags;
-	info->ops = &its_msi_domain_ops;
-	info->data = its;
-	inner_domain->host_data = info;
 
 	return 0;
 }