diff --git a/plat/arm/css/drivers/mhu/css_mhu.c b/plat/arm/css/drivers/mhu/css_mhu.c
new file mode 100644
index 0000000..30492a6
--- /dev/null
+++ b/plat/arm/css/drivers/mhu/css_mhu.c
@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch_helpers.h>
+#include <assert.h>
+#include <bakery_lock.h>
+#include <css_def.h>
+#include <mmio.h>
+#include <plat_arm.h>
+#include <platform_def.h>
+#include "css_mhu.h"
+
+/* SCP MHU secure channel registers */
+#define SCP_INTR_S_STAT		0x200
+#define SCP_INTR_S_SET		0x208
+#define SCP_INTR_S_CLEAR	0x210
+
+/* CPU MHU secure channel registers */
+#define CPU_INTR_S_STAT		0x300
+#define CPU_INTR_S_SET		0x308
+#define CPU_INTR_S_CLEAR	0x310
+
+ARM_INSTANTIATE_LOCK;
+
+/* Weak definition may be overridden in specific CSS based platform */
+#pragma weak plat_arm_pwrc_setup
+
+
+/*
+ * Slot 31 is reserved because the MHU hardware uses this register bit to
+ * indicate a non-secure access attempt. The total number of available slots is
+ * therefore 31 [30:0].
+ */
+#define MHU_MAX_SLOT_ID		30
+
+void mhu_secure_message_start(unsigned int slot_id)
+{
+	assert(slot_id <= MHU_MAX_SLOT_ID);
+
+	arm_lock_get();
+
+	/* Make sure any previous command has finished */
+	while (mmio_read_32(PLAT_CSS_MHU_BASE + CPU_INTR_S_STAT) &
+							(1 << slot_id))
+		;
+}
+
+void mhu_secure_message_send(unsigned int slot_id)
+{
+	assert(slot_id <= MHU_MAX_SLOT_ID);
+	assert(!(mmio_read_32(PLAT_CSS_MHU_BASE + CPU_INTR_S_STAT) &
+							(1 << slot_id)));
+
+	/* Send command to SCP */
+	mmio_write_32(PLAT_CSS_MHU_BASE + CPU_INTR_S_SET, 1 << slot_id);
+}
+
+uint32_t mhu_secure_message_wait(void)
+{
+	/* Wait for response from SCP */
+	uint32_t response;
+	while (!(response = mmio_read_32(PLAT_CSS_MHU_BASE + SCP_INTR_S_STAT)))
+		;
+
+	return response;
+}
+
+void mhu_secure_message_end(unsigned int slot_id)
+{
+	assert(slot_id <= MHU_MAX_SLOT_ID);
+
+	/*
+	 * Clear any response we got by writing one in the relevant slot bit to
+	 * the CLEAR register
+	 */
+	mmio_write_32(PLAT_CSS_MHU_BASE + SCP_INTR_S_CLEAR, 1 << slot_id);
+
+	arm_lock_release();
+}
+
+void mhu_secure_init(void)
+{
+	arm_lock_init();
+
+	/*
+	 * The STAT register resets to zero. Ensure it is in the expected state,
+	 * as a stale or garbage value would make us think it's a message we've
+	 * already sent.
+	 */
+	assert(mmio_read_32(PLAT_CSS_MHU_BASE + CPU_INTR_S_STAT) == 0);
+}
+
+void plat_arm_pwrc_setup(void)
+{
+	mhu_secure_init();
+}
diff --git a/plat/arm/css/drivers/mhu/css_mhu.h b/plat/arm/css/drivers/mhu/css_mhu.h
new file mode 100644
index 0000000..0fb00c7
--- /dev/null
+++ b/plat/arm/css/drivers/mhu/css_mhu.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __CSS_MHU_H__
+#define __CSS_MHU_H__
+
+#include <stdint.h>
+
+void mhu_secure_message_start(unsigned int slot_id);
+void mhu_secure_message_send(unsigned int slot_id);
+uint32_t mhu_secure_message_wait(void);
+void mhu_secure_message_end(unsigned int slot_id);
+
+void mhu_secure_init(void);
+
+#endif	/* __CSS_MHU_H__ */
diff --git a/plat/arm/css/drivers/mhu/css_mhu_doorbell.c b/plat/arm/css/drivers/mhu/css_mhu_doorbell.c
new file mode 100644
index 0000000..b9faf67
--- /dev/null
+++ b/plat/arm/css/drivers/mhu/css_mhu_doorbell.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch_helpers.h>
+#include <platform_def.h>
+#include "css_mhu_doorbell.h"
+#include "../scmi/scmi.h"
+
+void mhu_ring_doorbell(scmi_channel_plat_info_t *plat_info)
+{
+	MHU_RING_DOORBELL(plat_info->db_reg_addr,
+			plat_info->db_modify_mask,
+			plat_info->db_preserve_mask);
+	return;
+}
+
+void mhuv2_ring_doorbell(scmi_channel_plat_info_t *plat_info)
+{
+	/* wake receiver */
+	MHU_V2_ACCESS_REQUEST(MHUV2_BASE_ADDR);
+
+	/* wait for receiver to acknowledge its ready */
+	while (MHU_V2_IS_ACCESS_READY(MHUV2_BASE_ADDR) == 0)
+		;
+
+	MHU_RING_DOORBELL(plat_info->db_reg_addr,
+			plat_info->db_modify_mask,
+			plat_info->db_preserve_mask);
+
+	/* clear the access request for the recevier */
+	MHU_V2_CLEAR_REQUEST(MHUV2_BASE_ADDR);
+
+	return;
+}
diff --git a/plat/arm/css/drivers/mhu/css_mhu_doorbell.h b/plat/arm/css/drivers/mhu/css_mhu_doorbell.h
new file mode 100644
index 0000000..3c94536
--- /dev/null
+++ b/plat/arm/css/drivers/mhu/css_mhu_doorbell.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef CSS_MHU_DOORBELL_H
+#define CSS_MHU_DOORBELL_H
+
+#include <mmio.h>
+#include <stdint.h>
+
+/* MHUv2 Base Address */
+#define MHUV2_BASE_ADDR		PLAT_CSS_MHU_BASE
+
+/* MHUv2 Control Registers Offsets */
+#define MHU_V2_MSG_NO_CAP_OFFSET		0xF80
+#define MHU_V2_ACCESS_REQ_OFFSET		0xF88
+#define MHU_V2_ACCESS_READY_OFFSET		0xF8C
+
+#define SENDER_REG_STAT(CHANNEL)	(0x20 * (CHANNEL))
+#define SENDER_REG_SET(CHANNEL)		(0x20 * (CHANNEL)) + 0xC
+
+/* Helper macro to ring doorbell */
+#define MHU_RING_DOORBELL(addr, modify_mask, preserve_mask)	do {	\
+		uint32_t db = mmio_read_32(addr) & (preserve_mask);	\
+		mmio_write_32(addr, db | (modify_mask));		\
+	} while (0)
+
+#define MHU_V2_ACCESS_REQUEST(addr)	\
+	mmio_write_32((addr) + MHU_V2_ACCESS_REQ_OFFSET, 0x1)
+
+#define MHU_V2_CLEAR_REQUEST(addr)	\
+	mmio_write_32((addr) + MHU_V2_ACCESS_REQ_OFFSET, 0x0)
+
+#define MHU_V2_IS_ACCESS_READY(addr)	\
+	(mmio_read_32((addr) + MHU_V2_ACCESS_READY_OFFSET) & 0x1)
+
+struct scmi_channel_plat_info;
+void mhu_ring_doorbell(struct scmi_channel_plat_info *plat_info);
+void mhuv2_ring_doorbell(struct scmi_channel_plat_info *plat_info);
+
+#endif	/* CSS_MHU_DOORBELL_H */