diff --git a/doc/README.fdt-control b/doc/README.fdt-control
index c965629..378b06b 100644
--- a/doc/README.fdt-control
+++ b/doc/README.fdt-control
@@ -130,6 +130,10 @@
 CONFIG_SPL_FRAMEWORK, then u-boot.img will be built to include the device
 tree binary.
 
+If CONFIG_OF_BOARD is defined, a board-specific routine will provide the
+device tree at runtime, for example if an earlier bootloader stage creates
+it and passes it to U-Boot.
+
 If CONFIG_OF_HOSTFILE is defined, then it will be read from a file on
 startup. This is only useful for sandbox. Use the -d flag to U-Boot to
 specify the file to read.