of: Add cpu node iterator for_each_of_cpu_node()

Iterating thru cpu nodes is a common pattern. Create a common iterator
which can find child nodes either by node name or device_type == cpu.
Using the former will allow for eventually dropping device_type
properties which are deprecated for FDT.

Cc: Frank Rowand <frowand.list@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/include/linux/of.h b/include/linux/of.h
index 99b0ebf..1aca0db 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -353,6 +353,8 @@ extern const void *of_get_property(const struct device_node *node,
 				const char *name,
 				int *lenp);
 extern struct device_node *of_get_cpu_node(int cpu, unsigned int *thread);
+extern struct device_node *of_get_next_cpu_node(struct device_node *prev);
+
 #define for_each_property_of_node(dn, pp) \
 	for (pp = dn->properties; pp != NULL; pp = pp->next)
 
@@ -754,6 +756,11 @@ static inline struct device_node *of_get_cpu_node(int cpu,
 	return NULL;
 }
 
+static inline struct device_node *of_get_next_cpu_node(struct device_node *prev)
+{
+	return NULL;
+}
+
 static inline int of_n_addr_cells(struct device_node *np)
 {
 	return 0;
@@ -1217,6 +1224,10 @@ static inline int of_property_read_s32(const struct device_node *np,
 	for (child = of_get_next_available_child(parent, NULL); child != NULL; \
 	     child = of_get_next_available_child(parent, child))
 
+#define for_each_of_cpu_node(cpu) \
+	for (cpu = of_get_next_cpu_node(NULL); cpu != NULL; \
+	     cpu = of_get_next_cpu_node(cpu))
+
 #define for_each_node_with_property(dn, prop_name) \
 	for (dn = of_find_node_with_property(NULL, prop_name); dn; \
 	     dn = of_find_node_with_property(dn, prop_name))