diff --git a/include/lib/smccc.h b/include/lib/smccc.h
index 1a39f24..9940ea9 100644
--- a/include/lib/smccc.h
+++ b/include/lib/smccc.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -41,6 +41,8 @@
 #define FUNCID_NUM_MASK			U(0xffff)
 #define FUNCID_NUM_WIDTH		U(16)
 
+#define FUNCID_MASK			U(0xffffffff)
+
 #define GET_SMC_NUM(id)			(((id) >> FUNCID_NUM_SHIFT) & \
 					 FUNCID_NUM_MASK)
 #define GET_SMC_TYPE(id)		(((id) >> FUNCID_TYPE_SHIFT) & \
diff --git a/include/services/drtm_svc.h b/include/services/drtm_svc.h
new file mode 100644
index 0000000..6845ace
--- /dev/null
+++ b/include/services/drtm_svc.h
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2022 Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier:    BSD-3-Clause
+ *
+ * DRTM service
+ *
+ * Authors:
+ *	Lucian Paul-Trifu <lucian.paultrifu@gmail.com>
+ *	Brian Nezvadovitz <brinez@microsoft.com> 2021-02-01
+ *
+ */
+
+#ifndef ARM_DRTM_SVC_H
+#define ARM_DRTM_SVC_H
+
+/*
+ * SMC function IDs for DRTM Service
+ * Upper word bits set: Fast call, SMC64, Standard Secure Svc. Call (OEN = 4)
+ */
+#define DRTM_FID(func_num)				\
+	((SMC_TYPE_FAST << FUNCID_TYPE_SHIFT) |		\
+	(SMC_64 << FUNCID_CC_SHIFT) |			\
+	(OEN_STD_START << FUNCID_OEN_SHIFT) |		\
+	((func_num) << FUNCID_NUM_SHIFT))
+
+#define DRTM_FNUM_SVC_VERSION		U(0x110)
+#define DRTM_FNUM_SVC_FEATURES		U(0x111)
+#define DRTM_FNUM_SVC_UNPROTECT_MEM	U(0x113)
+#define DRTM_FNUM_SVC_DYNAMIC_LAUNCH	U(0x114)
+#define DRTM_FNUM_SVC_CLOSE_LOCALITY	U(0x115)
+#define DRTM_FNUM_SVC_GET_ERROR		U(0x116)
+#define DRTM_FNUM_SVC_SET_ERROR		U(0x117)
+#define DRTM_FNUM_SVC_SET_TCB_HASH	U(0x118)
+#define DRTM_FNUM_SVC_LOCK_TCB_HASH	U(0x119)
+
+#define ARM_DRTM_SVC_VERSION		DRTM_FID(DRTM_FNUM_SVC_VERSION)
+#define ARM_DRTM_SVC_FEATURES		DRTM_FID(DRTM_FNUM_SVC_FEATURES)
+#define ARM_DRTM_SVC_UNPROTECT_MEM	DRTM_FID(DRTM_FNUM_SVC_UNPROTECT_MEM)
+#define ARM_DRTM_SVC_DYNAMIC_LAUNCH	DRTM_FID(DRTM_FNUM_SVC_DYNAMIC_LAUNCH)
+#define ARM_DRTM_SVC_CLOSE_LOCALITY	DRTM_FID(DRTM_FNUM_SVC_CLOSE_LOCALITY)
+#define ARM_DRTM_SVC_GET_ERROR		DRTM_FID(DRTM_FNUM_SVC_GET_ERROR)
+#define ARM_DRTM_SVC_SET_ERROR		DRTM_FID(DRTM_FNUM_SVC_SET_ERROR)
+#define ARM_DRTM_SVC_SET_TCB_HASH	DRTM_FID(DRTM_FNUM_SVC_SET_TCB_HASH)
+#define ARM_DRTM_SVC_LOCK_TCB_HASH	DRTM_FID(DRTM_FNUM_SVC_LOCK_TCB_HASH)
+
+#define is_drtm_fid(_fid) \
+	(((_fid) >= ARM_DRTM_SVC_VERSION) && ((_fid) <= ARM_DRTM_SVC_LOCK_TCB_HASH))
+
+/* ARM DRTM Service Calls version numbers */
+#define ARM_DRTM_VERSION_MAJOR		U(0)
+#define ARM_DRTM_VERSION_MAJOR_SHIFT	16
+#define ARM_DRTM_VERSION_MAJOR_MASK	U(0x7FFF)
+#define ARM_DRTM_VERSION_MINOR		U(1)
+#define ARM_DRTM_VERSION_MINOR_SHIFT	0
+#define ARM_DRTM_VERSION_MINOR_MASK	U(0xFFFF)
+
+#define ARM_DRTM_VERSION						\
+	((((ARM_DRTM_VERSION_MAJOR) & ARM_DRTM_VERSION_MAJOR_MASK) <<	\
+	ARM_DRTM_VERSION_MAJOR_SHIFT)					\
+	| (((ARM_DRTM_VERSION_MINOR) & ARM_DRTM_VERSION_MINOR_MASK) <<	\
+	ARM_DRTM_VERSION_MINOR_SHIFT))
+
+#define ARM_DRTM_FUNC_SHIFT	U(63)
+#define ARM_DRTM_FUNC_MASK	U(0x1)
+#define ARM_DRTM_FUNC_ID	U(0x0)
+#define ARM_DRTM_FEAT_ID	U(0x1)
+
+/* Initialization routine for the DRTM service */
+int drtm_setup(void);
+
+/* Handler to be called to handle DRTM SMC calls */
+uint64_t drtm_smc_handler(uint32_t smc_fid,
+			  uint64_t x1,
+			  uint64_t x2,
+			  uint64_t x3,
+			  uint64_t x4,
+			  void *cookie,
+			  void *handle,
+			  uint64_t flags);
+
+#endif /* ARM_DRTM_SVC_H */