genirq: Introduce irq_domain_translate_onecell

Add a new function irq_domain_translate_onecell() that is to be used as
the translate function in struct irq_domain_ops.
Signed-off-by: Yash Shah <yash.shah@sifive.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1575976274-13487-2-git-send-email-yash.shah@sifive.com

include/linux/irqdomain.h

@@ -427,6 +427,11 @@ int irq_domain_translate_twocell(struct irq_domain *d,
 				 unsigned long *out_hwirq,
 				 unsigned int *out_type);
 
+int irq_domain_translate_onecell(struct irq_domain *d,
+				 struct irq_fwspec *fwspec,
+				 unsigned long *out_hwirq,
+				 unsigned int *out_type);
+
 /* IPI functions */
 int irq_reserve_ipi(struct irq_domain *domain, const struct cpumask *dest);
 int irq_destroy_ipi(unsigned int irq, const struct cpumask *dest);

kernel/irq/irqdomain.c

@@ -986,6 +986,23 @@ const struct irq_domain_ops irq_domain_simple_ops = {
 };
 EXPORT_SYMBOL_GPL(irq_domain_simple_ops);
 
+/**
+ * irq_domain_translate_onecell() - Generic translate for direct one cell
+ * bindings
+ */
+int irq_domain_translate_onecell(struct irq_domain *d,
+				 struct irq_fwspec *fwspec,
+				 unsigned long *out_hwirq,
+				 unsigned int *out_type)
+{
+	if (WARN_ON(fwspec->param_count < 1))
+		return -EINVAL;
+	*out_hwirq = fwspec->param[0];
+	*out_type = IRQ_TYPE_NONE;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(irq_domain_translate_onecell);
+
 /**
  * irq_domain_translate_twocell() - Generic translate for direct two cell
  * bindings