diff --git a/docs/porting-guide.rst b/docs/porting-guide.rst
index f020ec9..402cc5d 100644
--- a/docs/porting-guide.rst
+++ b/docs/porting-guide.rst
@@ -1128,6 +1128,9 @@
 for performing any remaining platform-specific setup that can occur after the
 MMU and data cache have been enabled.
 
+if support for multiple boot sources is required, it initializes the boot
+sequence used by plat\_try\_next\_boot\_source().
+
 In ARM standard platforms, this function initializes the storage abstraction
 layer used to load the next bootloader image.