Allow references to labels

dtc allows nodes to have labels, which at present are just re-emitted
as symbols at the appropriate places when using asm-mode output.  It
also allows "references" where the notation &/path/to/node in a cell
list will be replaced with the phandle of the referenced node.

This patch extends the reference syntax to allow references to labels
instead of just full device paths.  This allows nodes deep within the
tree to be referenced with a shorter more convenient name.  References
to labels are distinguished from reference to paths by the fact that
paths must start with a /, but labels can never start with a /.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Jon Loeliger <jdl@freescale.com>

livetree.c

@@ -212,6 +212,24 @@ static struct node *get_node_by_path(struct node *tree, char *path)
 	return NULL;
 }
 
+static struct node *get_node_by_label(struct node *tree, const char *label)
+{
+	struct node *child, *node;
+
+	assert(label && (strlen(label) > 0));
+
+	if (tree->label && streq(tree->label, label))
+		return tree;
+
+	for_each_child(tree, child) {
+		node = get_node_by_label(child, label);
+		if (node)
+			return node;
+	}
+
+	return NULL;
+}
+
 static struct node *get_node_by_phandle(struct node *tree, cell_t phandle)
 {
 	struct node *child, *node;	
@@ -229,6 +247,7 @@ static struct node *get_node_by_phandle(struct node *tree, cell_t phandle)
 
 	return NULL;
 }
+
 /*
  * Tree checking functions
  */
@@ -673,9 +692,16 @@ static void apply_fixup(struct node *root, struct property *prop,
 	struct node *refnode;
 	cell_t phandle;
 
+	if (f->ref[0] == '/') {
+		/* Reference to full path */
 		refnode = get_node_by_path(root, f->ref);
 		if (! refnode)
 			die("Reference to non-existent node \"%s\"\n", f->ref);
+	} else {
+		refnode = get_node_by_label(root, f->ref);
+		if (! refnode)
+			die("Reference to non-existent node label \"%s\"\n", f->ref);
+	}
 
 	phandle = get_node_phandle(root, refnode);