improve carrier id documentation
Bug: 126440877
Test: Build
Change-Id: Icc91f145f0c804595ea4e35ade2a1ab6d99fcb1f
diff --git a/assets/README b/assets/README
new file mode 100644
index 0000000..ad6a29c
--- /dev/null
+++ b/assets/README
@@ -0,0 +1,12 @@
+====== carrier_list.textpb ======
+
+DO NOT MANUALLY EDIT THIS FILE
+
+This file is the textpb verion of carrier_list.pb files under assets/, for readability purpose only.
+
+This file is not build into pb, thus modification of this file won't take any effect.
+
+===== carrier_list.pb =====
+DO NOT MANUALLY EDIT THIS FILE
+
+This file defines carrier id and should be single versioned.
