dt: add of_alias_scan and of_alias_get_id

The patch adds function of_alias_scan to populate a global lookup
table with the properties of 'aliases' node and function
of_alias_get_id for drivers to find alias id from the lookup table.

v3: Split out automatic addition of aliases on id lookup so that it can be
    debated separately from the core functionality.
v2: - Add of_chosen/of_aliases populating and of_alias_scan() invocation
    for OF_PROMTREE.
    - Add locking
    - rework parse loop

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 65200af..aeec35b 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -707,10 +707,8 @@
 	__unflatten_device_tree(initial_boot_params, &allnodes,
 				early_init_dt_alloc_memory_arch);
 
-	/* Get pointer to OF "/chosen" node for use everywhere */
-	of_chosen = of_find_node_by_path("/chosen");
-	if (of_chosen == NULL)
-		of_chosen = of_find_node_by_path("/chosen@0");
+	/* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
+	of_alias_scan(early_init_dt_alloc_memory_arch);
 }
 
 #endif /* CONFIG_OF_EARLY_FLATTREE */