fdtoverlay: Ignore symbols in overlays which don't apply to the target tree

Symbols from overlays are merged into the target tree, and are required to
have the form:
	/fragment@XXX/__overlay__/...
If any symbols don't have this form, the overlay is rejected.

But there's not really anything wrong with an overlay having "local"
labels referring to a fragment node or some other metadata, that's not
expected to end up in a target tree.

So change our overlay application to simply ignore such symbols rather than
fail.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/fdt_overlay.c

@@ -738,8 +738,11 @@ static int overlay_symbol_update(void *fdt, void *fdto)
 
 		/* get fragment name first */
 		s = strchr(path + 1, '/');
-		if (!s)
-			return -FDT_ERR_BADOVERLAY;
+		if (!s) {
+			/* Symbol refers to something that won't end
+			 * up in the target tree */
+			continue;
+		}
 
 		frag_name = path + 1;
 		frag_name_len = s - path - 1;
@@ -756,7 +759,9 @@ static int overlay_symbol_update(void *fdt, void *fdto)
 			rel_path = "";
 			rel_path_len = 0;
 		} else {
-			return -FDT_ERR_BADOVERLAY;
+			/* Symbol refers to something that won't end
+			 * up in the target tree */
+			continue;
 		}
 
 		/* find the fragment index in which the symbol lies */

tests/stacked_overlay_addlabel.dts

@@ -1,8 +1,10 @@
 /dts-v1/;
 /plugin/;
 / {
-	fragment@1 {
+	frag1: fragment@1 {
 		target-path = "/foonode";
+		local: localinfo {
+		};
 		foo: __overlay__ {
 			overlay-1-property;
 			bar: barnode {