diff --git a/plat/arm/css/drivers/scmi/scmi.h b/plat/arm/css/drivers/scmi/scmi.h
new file mode 100644
index 0000000..850402a
--- /dev/null
+++ b/plat/arm/css/drivers/scmi/scmi.h
@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __CSS_SCMI_H__
+#define __CSS_SCMI_H__
+
+#include <bakery_lock.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/* Supported SCMI Protocol Versions */
+#define SCMI_PWR_DMN_PROTO_VER			MAKE_SCMI_VERSION(1, 0)
+#define SCMI_SYS_PWR_PROTO_VER			MAKE_SCMI_VERSION(1, 0)
+
+#define GET_SCMI_MAJOR_VER(ver)			(((ver) >> 16) & 0xffff)
+#define GET_SCMI_MINOR_VER(ver)			((ver) & 0xffff)
+
+#define MAKE_SCMI_VERSION(maj, min)	\
+			((((maj) & 0xffff) << 16) | ((min) & 0xffff))
+
+/* Macro to check if the driver is compatible with the SCMI version reported */
+#define is_scmi_version_compatible(drv, scmi)				\
+	((GET_SCMI_MAJOR_VER(drv) == GET_SCMI_MAJOR_VER(scmi)) &&	\
+	(GET_SCMI_MINOR_VER(drv) <= GET_SCMI_MINOR_VER(scmi)))
+
+/* SCMI Protocol identifiers */
+#define SCMI_PWR_DMN_PROTO_ID			0x11
+#define SCMI_SYS_PWR_PROTO_ID			0x12
+
+/* Mandatory messages IDs for all SCMI protocols */
+#define SCMI_PROTO_VERSION_MSG			0x0
+#define SCMI_PROTO_ATTR_MSG			0x1
+#define SCMI_PROTO_MSG_ATTR_MSG			0x2
+
+/* SCMI power domain management protocol message IDs */
+#define SCMI_PWR_STATE_SET_MSG			0x4
+#define SCMI_PWR_STATE_GET_MSG			0x5
+
+/* SCMI system power management protocol message IDs */
+#define SCMI_SYS_PWR_STATE_SET_MSG		0x3
+#define SCMI_SYS_PWR_STATE_GET_MSG		0x4
+
+/* Helper macros for system power management protocol commands */
+
+/*
+ * Macros to describe the bit-fields of the `attribute` of system power domain
+ * protocol PROTOCOL_MSG_ATTRIBUTE message.
+ */
+#define SYS_PWR_ATTR_WARM_RESET_SHIFT		31
+#define SCMI_SYS_PWR_WARM_RESET_SUPPORTED	(1U << SYS_PWR_ATTR_WARM_RESET_SHIFT)
+
+#define SYS_PWR_ATTR_SUSPEND_SHIFT		30
+#define SCMI_SYS_PWR_SUSPEND_SUPPORTED		(1 << SYS_PWR_ATTR_SUSPEND_SHIFT)
+
+/*
+ * Macros to describe the bit-fields of the `flags` parameter of system power
+ * domain protocol SYSTEM_POWER_STATE_SET message.
+ */
+#define SYS_PWR_SET_GRACEFUL_REQ_SHIFT		0
+#define SCMI_SYS_PWR_GRACEFUL_REQ		(1 << SYS_PWR_SET_GRACEFUL_REQ_SHIFT)
+#define SCMI_SYS_PWR_FORCEFUL_REQ		(0 << SYS_PWR_SET_GRACEFUL_REQ_SHIFT)
+
+/*
+ * Macros to describe the `system_state` parameter of system power
+ * domain protocol SYSTEM_POWER_STATE_SET message.
+ */
+#define SCMI_SYS_PWR_SHUTDOWN			0x0
+#define SCMI_SYS_PWR_COLD_RESET			0x1
+#define SCMI_SYS_PWR_WARM_RESET			0x2
+#define SCMI_SYS_PWR_POWER_UP			0x3
+#define SCMI_SYS_PWR_SUSPEND			0x4
+
+/* SCMI Error code definitions */
+#define SCMI_E_QUEUED			1
+#define SCMI_E_SUCCESS			0
+#define SCMI_E_NOT_SUPPORTED		-1
+#define SCMI_E_INVALID_PARAM		-2
+#define SCMI_E_DENIED			-3
+#define SCMI_E_NOT_FOUND		-4
+#define SCMI_E_OUT_OF_RANGE		-5
+#define SCMI_E_BUSY			-6
+
+/*
+ * SCMI driver platform information. The details of the doorbell mechanism
+ * can be found in the SCMI specification.
+ */
+typedef struct scmi_channel_plat_info {
+	/* SCMI mailbox memory */
+	uintptr_t scmi_mbx_mem;
+	/* The door bell register address */
+	uintptr_t db_reg_addr;
+	/* The bit mask that need to be preserved when ringing doorbell */
+	uint32_t db_preserve_mask;
+	/* The bit mask that need to be set to ring doorbell */
+	uint32_t db_modify_mask;
+} scmi_channel_plat_info_t;
+
+/*
+ * Structure to represent an SCMI channel.
+ */
+typedef struct scmi_channel {
+	scmi_channel_plat_info_t *info;
+	 /* The lock for channel access */
+	bakery_lock_t *lock;
+	/* Indicate whether the channel is initialized */
+	int is_initialized;
+} scmi_channel_t;
+
+/* External Common API */
+void *scmi_init(scmi_channel_t *ch);
+int scmi_proto_msg_attr(void *p, uint32_t proto_id, uint32_t command_id,
+						uint32_t *attr);
+int scmi_proto_version(void *p, uint32_t proto_id, uint32_t *version);
+
+/*
+ * Power domain protocol commands. Refer to the SCMI specification for more
+ * details on these commands.
+ */
+int scmi_pwr_state_set(void *p, uint32_t domain_id, uint32_t scmi_pwr_state);
+int scmi_pwr_state_get(void *p, uint32_t domain_id, uint32_t *scmi_pwr_state);
+
+/*
+ * System power management protocol commands. Refer SCMI specification for more
+ * details on these commands.
+ */
+int scmi_sys_pwr_state_set(void *p, uint32_t flags, uint32_t system_state);
+int scmi_sys_pwr_state_get(void *p, uint32_t *system_state);
+
+#endif	/* __CSS_SCMI_H__ */