diff --git a/drivers/st/scmi-msg/common.h b/drivers/st/scmi-msg/common.h
new file mode 100644
index 0000000..4777dbe
--- /dev/null
+++ b/drivers/st/scmi-msg/common.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Copyright (c) 2015-2019, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2019-2020, Linaro Limited
+ */
+#ifndef SCMI_MSG_COMMON_H
+#define SCMI_MSG_COMMON_H
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "base.h"
+
+#define SCMI_VERSION			0x20000U
+#define SCMI_IMPL_VERSION		0U
+
+#define SCMI_PLAYLOAD_MAX		92U
+
+/*
+ * Copy name identifier in target buffer following the SCMI specification
+ * that state name identifier shall be a null terminated string.
+ */
+#define COPY_NAME_IDENTIFIER(_dst_array, _name)				\
+	do {								\
+		assert(strlen(_name) < sizeof(_dst_array));		\
+		strlcpy((_dst_array), (_name), sizeof(_dst_array));	\
+	} while (0)
+
+/* Common command identifiers shared by all procotols */
+enum scmi_common_message_id {
+	SCMI_PROTOCOL_VERSION = 0x000,
+	SCMI_PROTOCOL_ATTRIBUTES = 0x001,
+	SCMI_PROTOCOL_MESSAGE_ATTRIBUTES = 0x002
+};
+
+/* Common platform-to-agent (p2a) PROTOCOL_VERSION structure */
+struct scmi_protocol_version_p2a {
+	int32_t status;
+	uint32_t version;
+};
+
+/* Generic platform-to-agent (p2a) PROTOCOL_ATTRIBUTES structure */
+struct scmi_protocol_attributes_p2a {
+	int32_t status;
+	uint32_t attributes;
+};
+
+/* Generic agent-to-platform (a2p) PROTOCOL_MESSAGE_ATTRIBUTES structure */
+struct scmi_protocol_message_attributes_a2p {
+	uint32_t message_id;
+};
+
+/* Generic platform-to-agent (p2a) PROTOCOL_MESSAGE_ATTRIBUTES structure */
+struct scmi_protocol_message_attributes_p2a {
+	int32_t status;
+	uint32_t attributes;
+};
+
+/*
+ * struct scmi_msg - SCMI message context
+ *
+ * @agent_id: SCMI agent ID, safely set from secure world
+ * @protocol_id: SCMI protocol ID for the related message, set by caller agent
+ * @message_id: SCMI message ID for the related message, set by caller agent
+ * @in: Address of the incoming message payload copied in secure memory
+ * @in_size: Byte length of the incoming message payload, set by caller agent
+ * @out: Address of of the output message payload message in non-secure memory
+ * @out_size: Byte length of the provisionned output buffer
+ * @out_size_out: Byte length of the output message payload
+ */
+struct scmi_msg {
+	unsigned int agent_id;
+	unsigned int protocol_id;
+	unsigned int message_id;
+	char *in;
+	size_t in_size;
+	char *out;
+	size_t out_size;
+	size_t out_size_out;
+};
+
+/*
+ * Type scmi_msg_handler_t is used by procotol drivers to safely find
+ * the handler function for the incoming message ID.
+ */
+typedef void (*scmi_msg_handler_t)(struct scmi_msg *msg);
+
+/*
+ * scmi_msg_get_base_handler - Return a handler for a base message
+ * @msg - message to process
+ * Return a function handler for the message or NULL
+ */
+scmi_msg_handler_t scmi_msg_get_base_handler(struct scmi_msg *msg);
+
+/*
+ * Process Read, process and write response for input SCMI message
+ *
+ * @msg: SCMI message context
+ */
+void scmi_process_message(struct scmi_msg *msg);
+
+/*
+ * Write SCMI response payload to output message shared memory
+ *
+ * @msg: SCMI message context
+ * @payload: Output message payload
+ * @size: Byte size of output message payload
+ */
+void scmi_write_response(struct scmi_msg *msg, void *payload, size_t size);
+
+/*
+ * Write status only SCMI response payload to output message shared memory
+ *
+ * @msg: SCMI message context
+ * @status: SCMI status value returned to caller
+ */
+void scmi_status_response(struct scmi_msg *msg, int32_t status);
+#endif /* SCMI_MSG_COMMON_H */