irqdomain: Fix kernel-doc and add it to Documentation

irqdomain.c's kernel-doc exists, but is not plugged into Documentation/
yet.

Before plugging it in, fix it first: irq_domain_get_irq_data() and
irq_domain_set_info() were documented twice. Identically, by both
definitions for CONFIG_IRQ_DOMAIN_HIERARCHY and !CONFIG_IRQ_DOMAIN_HIERARCHY.

Therefore, switch the second kernel-doc into an ordinary comment -- change
"/**" to simple "/*". This avoids sphinx's: WARNING: Duplicate C
declaration

Next, in commit b7b377332b ("irqdomain: Fix the kernel-doc and plug it
into Documentation"), irqdomain.h's (header) kernel-doc was added into
core-api/genericirq.rst. But given the amount of irqdomain functions and
structures, move all these to core-api/irq/irq-domain.rst now.

Finally, add these newly fixed irqdomain.c's (source) docs there as
well.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250319092951.37667-58-jirislaby@kernel.org

Documentation/core-api/genericirq.rst

@@ -410,8 +410,6 @@ which are used in the generic IRQ layer.
 .. kernel-doc:: include/linux/interrupt.h
    :internal:
 
-.. kernel-doc:: include/linux/irqdomain.h
-
 Public Functions Provided
 =========================
 

Documentation/core-api/irq/irq-domain.rst

@@ -298,3 +298,23 @@ Debugging
 
 Most of the internals of the IRQ subsystem are exposed in debugfs by
 turning CONFIG_GENERIC_IRQ_DEBUGFS on.
+
+Structures and Public Functions Provided
+========================================
+
+This chapter contains the autogenerated documentation of the structures
+and exported kernel API functions which are used for IRQ domains.
+
+.. kernel-doc:: include/linux/irqdomain.h
+
+.. kernel-doc:: kernel/irq/irqdomain.c
+   :export:
+
+Internal Functions Provided
+===========================
+
+This chapter contains the autogenerated documentation of the internal
+functions.
+
+.. kernel-doc:: kernel/irq/irqdomain.c
+   :internal:

kernel/irq/irqdomain.c

@@ -1996,7 +1996,7 @@ static void irq_domain_check_hierarchy(struct irq_domain *domain)
 		domain->flags |= IRQ_DOMAIN_FLAG_HIERARCHY;
 }
 #else	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
-/**
+/*
  * irq_domain_get_irq_data - Get irq_data associated with @virq and @domain
  * @domain:	domain to match
  * @virq:	IRQ number to get irq_data
@@ -2010,7 +2010,7 @@ struct irq_data *irq_domain_get_irq_data(struct irq_domain *domain,
 }
 EXPORT_SYMBOL_GPL(irq_domain_get_irq_data);
 
-/**
+/*
  * irq_domain_set_info - Set the complete data for a @virq in @domain
  * @domain:		Interrupt domain to match
  * @virq:		IRQ number