diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 5980050..68ef4ce 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -851,6 +851,9 @@
    hardware will limit the effective VL to the maximum physically supported
    VL.
 
+-  ``TRNG_SUPPORT``: Setting this to ``1`` enables support for True
+   Random Number Generator Interface to BL31 image. This defaults to ``0``.
+
 -  ``TRUSTED_BOARD_BOOT``: Boolean flag to include support for the Trusted Board
    Boot feature. When set to '1', BL1 and BL2 images include support to load
    and verify the certificates and images in a FIP, and BL1 includes support