binman: Support an entry that holds text

It is useful to able to write an identifying string to the image within an
entry. Add a 'text' entry type to handle this. The actual text is
typically passed to binman on the command line. The text is not itself
nul-terminated but this can be achieved if required by setting the size of
the entry to something larger than the text.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/test/66_text.dts b/tools/binman/test/66_text.dts
new file mode 100644
index 0000000..59b1fed
--- /dev/null
+++ b/tools/binman/test/66_text.dts
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0+
+/dts-v1/;
+
+/ {
+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	binman {
+		text {
+			size = <8>;
+			text-label = "test-id";
+		};
+		text2 {
+			type = "text";
+			text-label = "test-id2";
+		};
+		text3 {
+			type = "text";
+			text-label = "test-id3";
+		};
+		/* This one does not use command-line args */
+		text4 {
+			type = "text";
+			text-label = "test-id4";
+			test-id4 = "some text";
+		};
+	};
+};