dtc: Plugin and fixup support

This patch enable the generation of symbols & local fixup information
for trees compiled with the -@ (--symbols) option.

Using this patch labels in the tree and their users emit information
in __symbols__ and __local_fixups__ nodes.

The __fixups__ node make possible the dynamic resolution of phandle
references which are present in the plugin tree but lie in the
tree that are applying the overlay against.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Documentation/manual.txt

@@ -119,6 +119,20 @@ Options:
 	Make space for <number> reserve map entries
 	Relevant for dtb and asm output only.
 
+    -@
+	Generates a __symbols__ node at the root node of the resulting blob
+	for any node labels used, and for any local references using phandles
+	it also generates a __local_fixups__ node that tracks them.
+
+	When using the /plugin/ tag all unresolved label references to
+	be tracked in the __fixups__ node, making dynamic resolution possible.
+
+    -A
+	Generate automatically aliases for all node labels. This is similar to
+	the -@ option (the __symbols__ node contain identical information) but
+	the semantics are slightly different since no phandles are automatically
+	generated for labeled nodes.
+
     -S <bytes>
 	Ensure the blob at least <bytes> long, adding additional
 	space if needed.
@@ -146,13 +160,18 @@ Additionally, dtc performs various sanity checks on the tree.
 Here is a very rough overview of the layout of a DTS source file:
 
 
-    sourcefile:   list_of_memreserve devicetree
+    sourcefile:   versioninfo plugindecl list_of_memreserve devicetree
 
     memreserve:   label 'memreserve' ADDR ADDR ';'
 		| label 'memreserve' ADDR '-' ADDR ';'
 
     devicetree:   '/' nodedef
 
+    versioninfo:  '/' 'dts-v1' '/' ';'
+
+    plugindecl:   '/' 'plugin' '/' ';'
+                | /* empty */
+
     nodedef:      '{' list_of_property list_of_subnode '}' ';'
 
     property:     label PROPNAME '=' propdata ';'