irqdomain: Make of_phandle_args_to_fwspec() generally available

of_phandle_args_to_fwspec() can be generally useful to code extracting a DT
of_phandle and using an irq_fwspec to use the hierarchical irqdomain API.

Make it visible to the rest of the kernel, including modules.

Link: https://lore.kernel.org/r/20210929163847.2807812-2-maz@kernel.orgTested-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

include/linux/irqdomain.h

@@ -64,6 +64,10 @@ struct irq_fwspec {
 	u32 param[IRQ_DOMAIN_IRQ_SPEC_PARAMS];
 };
 
+/* Conversion function from of_phandle_args fields to fwspec  */
+void of_phandle_args_to_fwspec(struct device_node *np, const u32 *args,
+			       unsigned int count, struct irq_fwspec *fwspec);
+
 /*
  * Should several domains have the same device node, but serve
  * different purposes (for example one domain is for PCI/MSI, and the

kernel/irq/irqdomain.c

@@ -744,9 +744,8 @@ static int irq_domain_translate(struct irq_domain *d,
 	return 0;
 }
 
-static void of_phandle_args_to_fwspec(struct device_node *np, const u32 *args,
-				      unsigned int count,
-				      struct irq_fwspec *fwspec)
+void of_phandle_args_to_fwspec(struct device_node *np, const u32 *args,
+			       unsigned int count, struct irq_fwspec *fwspec)
 {
 	int i;
 
@@ -756,6 +755,7 @@ static void of_phandle_args_to_fwspec(struct device_node *np, const u32 *args,
 	for (i = 0; i < count; i++)
 		fwspec->param[i] = args[i];
 }
+EXPORT_SYMBOL_GPL(of_phandle_args_to_fwspec);
 
 unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
 {