Documentation/IRQ-domain.txt: Document irq_domain_create_{linear, tree}

They have the same functionalities as irq_domain_add_{linear, tree},
except fro accepting different first argument.

Signed-off-by: Jianyu Zhan <[e-mail]>
Acked-by: Marc Zyngier <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/IRQ-domain.txt

···
 
 ==== Linear ====
 irq_domain_add_linear()
+irq_domain_create_linear()
 
 The linear reverse map maintains a fixed size table indexed by the
 hwirq number.  When a hwirq is mapped, an irq_desc is allocated for
···
 allocated for in-use IRQs.  The disadvantage is that the table must be
 as large as the largest possible hwirq number.
 
+irq_domain_add_linear() and irq_domain_create_linear() are functionally
+equivalent, except for the first argument is different - the former
+accepts an Open Firmware specific 'struct device_node', while the latter
+accepts a more general abstraction 'struct fwnode_handle'.
+
 The majority of drivers should use the linear map.
 
 ==== Tree ====
 irq_domain_add_tree()
+irq_domain_create_tree()
 
 The irq_domain maintains a radix tree map from hwirq numbers to Linux
 IRQs.  When an hwirq is mapped, an irq_desc is allocated and the
···
 since it doesn't need to allocate a table as large as the largest
 hwirq number.  The disadvantage is that hwirq to IRQ number lookup is
 dependent on how many entries are in the table.
+
+irq_domain_add_tree() and irq_domain_create_tree() are functionally
+equivalent, except for the first argument is different - the former
+accepts an Open Firmware specific 'struct device_node', while the latter
+accepts a more general abstraction 'struct fwnode_handle'.
 
 Very few drivers should need this mapping.