diff --git a/docs/getting_started/porting-guide.rst b/docs/getting_started/porting-guide.rst
index d935436..3d3b2e3 100644
--- a/docs/getting_started/porting-guide.rst
+++ b/docs/getting_started/porting-guide.rst
@@ -2043,6 +2043,32 @@
 
 The function returns 0 on success, -EINVAL on failure.
 
+Function : plat_get_cca_realm_attest_key() [mandatory when ENABLE_RME == 1]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+::
+
+    Argument : uintptr_t, size_t *, unsigned int
+    Return   : int
+
+This function returns the delegated realm attestation key which will be used to
+sign Realm attestation token. The API currently only supports P-384 ECC curve
+key.
+
+The parameters of the function are:
+
+    arg0 - A pointer to the buffer where the attestation key should be copied
+           by this function. The buffer must be big enough to hold the
+           attestation key.
+
+    arg1 - Contains the size (in bytes) of the buffer passed in arg0. The
+           function returns the attestation key length in this parameter.
+
+    arg2 - The type of the elliptic curve to which the requested attestation key
+           belongs.
+
+The function returns 0 on success, -EINVAL on failure.
+
 Function : bl31_plat_enable_mmu [optional]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -3180,7 +3206,7 @@
 
 --------------
 
-*Copyright (c) 2013-2021, Arm Limited and Contributors. All rights reserved.*
+*Copyright (c) 2013-2022, Arm Limited and Contributors. All rights reserved.*
 
 .. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022c/DEN0022C_Power_State_Coordination_Interface.pdf
 .. _Arm Generic Interrupt Controller version 2.0 (GICv2): http://infocenter.arm.com/help/topic/com.arm.doc.ihi0048b/index.html