genirq: Clarify documentation for request_threaded_irq()

Clarify wording and document commonly used IRQF_ONESHOT flag.
Signed-off-by: Joel Savitz <jsavitz@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210731050740.444454-1-jsavitz@redhat.com

kernel/irq/manage.c

@@ -2072,9 +2072,9 @@ const void *free_nmi(unsigned int irq, void *dev_id)
  *	request_threaded_irq - allocate an interrupt line
  *	@irq: Interrupt line to allocate
  *	@handler: Function to be called when the IRQ occurs.
- *		  Primary handler for threaded interrupts
- *		  If NULL and thread_fn != NULL the default
- *		  primary handler is installed
+ *		  Primary handler for threaded interrupts.
+ *		  If handler is NULL and thread_fn != NULL
+ *		  the default primary handler is installed.
  *	@thread_fn: Function called from the irq handler thread
  *		    If NULL, no irq thread is created
  *	@irqflags: Interrupt type flags
@@ -2108,6 +2108,8 @@ const void *free_nmi(unsigned int irq, void *dev_id)
  *
  *	IRQF_SHARED		Interrupt is shared
  *	IRQF_TRIGGER_*		Specify active edge(s) or level
+ *	IRQF_ONESHOT		Do not unmask interrupt line until
+ *				thread_fn returns
  *
  */
 int request_threaded_irq(unsigned int irq, irq_handler_t handler,