binman: Add an FDT map

An FDT map is an entry which holds a full description of the image
entries, in FDT format. It can be discovered using the magic string at
its start. Tools can locate and read this entry to find out what entries
are in the image and where each entry is located.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/test/115_fdtmap.dts b/tools/binman/test/115_fdtmap.dts
new file mode 100644
index 0000000..2450c41
--- /dev/null
+++ b/tools/binman/test/115_fdtmap.dts
@@ -0,0 +1,13 @@
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		u-boot {
+		};
+		fdtmap {
+		};
+	};
+};