diff --git a/docs/plat/arm/arm-build-options.rst b/docs/plat/arm/arm-build-options.rst
index db8d945..d4fa98d 100644
--- a/docs/plat/arm/arm-build-options.rst
+++ b/docs/plat/arm/arm-build-options.rst
@@ -104,6 +104,9 @@
    device tree. This flag is defined only when ``ARM_SPMC_MANIFEST_DTS`` manifest
    file name contains pattern optee_sp.
 
+-  ``TS_SP_FW_CONFIG``: DTC build flag to include Trusted Services (Crypto and
+   secure-storage) as SP in tb_fw_config device tree.
+
 -  ``ARM_GPT_SUPPORT``: Enable GPT parser to get the entry address and length of
    the various partitions present in the GPT image. This support is available
    only for the BL2 component, and it is disabled by default.