irqdomain: Improve kernel-docs of functions

Many of irqdomain.h's functions are referenced in Documentation/ but are
not properly documented. Therefore, document these.

And use "Returns:" tag consistently, so that it is properly generated in
the resulting docs.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250319092951.37667-53-jirislaby@kernel.org

Author: Jiri Slaby (SUSE)

include/linux/irqdomain.h

@@ -411,6 +411,15 @@ static inline struct irq_domain *irq_domain_create_nomap(struct fwnode_handle *f
 unsigned int irq_create_direct_mapping(struct irq_domain *domain);
 #endif
 
+/**
+ * irq_domain_create_linear - Allocate and register a linear revmap irq_domain.
+ * @fwnode: pointer to interrupt controller's FW node.
+ * @size: Number of interrupts in the domain.
+ * @ops: map/unmap domain callbacks
+ * @host_data: Controller private data pointer
+ *
+ * Returns: Newly created irq_domain
+ */
 static inline struct irq_domain *irq_domain_create_linear(struct fwnode_handle *fwnode,
 					 unsigned int size,
 					 const struct irq_domain_ops *ops,
@@ -457,6 +466,18 @@ unsigned int irq_create_mapping_affinity(struct irq_domain *domain,
 unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec);
 void irq_dispose_mapping(unsigned int virq);
 
+/**
+ * irq_create_mapping - Map a hardware interrupt into linux irq space
+ * @domain: domain owning this hardware interrupt or NULL for default domain
+ * @hwirq: hardware irq number in that domain space
+ *
+ * Only one mapping per hardware interrupt is permitted.
+ *
+ * If the sense/trigger is to be specified, set_irq_type() should be called
+ * on the number returned from that call.
+ *
+ * Returns: Linux irq number or 0 on error
+ */
 static inline unsigned int irq_create_mapping(struct irq_domain *domain,
 					      irq_hw_number_t hwirq)
 {
@@ -467,6 +488,13 @@ struct irq_desc *__irq_resolve_mapping(struct irq_domain *domain,
 				       irq_hw_number_t hwirq,
 				       unsigned int *irq);
 
+/**
+ * irq_resolve_mapping - Find a linux irq from a hw irq number.
+ * @domain: domain owning this hardware interrupt
+ * @hwirq: hardware irq number in that domain space
+ *
+ * Returns: Interrupt descriptor
+ */
 static inline struct irq_desc *irq_resolve_mapping(struct irq_domain *domain,
 						   irq_hw_number_t hwirq)
 {
@@ -477,6 +505,8 @@ static inline struct irq_desc *irq_resolve_mapping(struct irq_domain *domain,
  * irq_find_mapping() - Find a linux irq from a hw irq number.
  * @domain: domain owning this hardware interrupt
  * @hwirq: hardware irq number in that domain space
+ *
+ * Returns: Linux irq number or 0 if not found
  */
 static inline unsigned int irq_find_mapping(struct irq_domain *domain,
 					    irq_hw_number_t hwirq)
@@ -539,7 +569,8 @@ void irq_domain_reset_irq_data(struct irq_data *irq_data);
  *
  * If successful the parent is associated to the new domain and the
  * domain flags are set.
- * Returns pointer to IRQ domain, or NULL on failure.
+ *
+ * Returns: A pointer to IRQ domain, or %NULL on failure.
  */
 static inline struct irq_domain *irq_domain_create_hierarchy(struct irq_domain *parent,
 					    unsigned int flags,
@@ -570,6 +601,15 @@ void irq_domain_free_irqs(unsigned int virq, unsigned int nr_irqs);
 int irq_domain_activate_irq(struct irq_data *irq_data, bool early);
 void irq_domain_deactivate_irq(struct irq_data *irq_data);
 
+/**
+ * irq_domain_alloc_irqs - Allocate IRQs from domain
+ * @domain:	domain to allocate from
+ * @nr_irqs:	number of IRQs to allocate
+ * @node:	NUMA node id for memory allocation
+ * @arg:	domain specific argument
+ *
+ * See __irq_domain_alloc_irqs()' documentation.
+ */
 static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
 			unsigned int nr_irqs, int node, void *arg)
 {