diff --git a/drivers/arm/css/mhu/css_mhu.c b/drivers/arm/css/mhu/css_mhu.c
new file mode 100644
index 0000000..b7faf7e
--- /dev/null
+++ b/drivers/arm/css/mhu/css_mhu.c
@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+
+#include <platform_def.h>
+
+#include <arch_helpers.h>
+#include <drivers/arm/css/css_mhu.h>
+#include <lib/bakery_lock.h>
+#include <lib/mmio.h>
+#include <plat/arm/common/plat_arm.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 __init 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 __init plat_arm_pwrc_setup(void)
+{
+	mhu_secure_init();
+}
diff --git a/drivers/arm/css/mhu/css_mhu_doorbell.c b/drivers/arm/css/mhu/css_mhu_doorbell.c
new file mode 100644
index 0000000..8858742
--- /dev/null
+++ b/drivers/arm/css/mhu/css_mhu_doorbell.c
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2014-2019, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <platform_def.h>
+
+#include <arch_helpers.h>
+#include <drivers/arm/css/css_mhu_doorbell.h>
+#include <drivers/arm/css/scmi.h>
+
+void mhu_ring_doorbell(struct scmi_channel_plat_info *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(struct scmi_channel_plat_info *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 receiver */
+	MHU_V2_CLEAR_REQUEST(MHUV2_BASE_ADDR);
+
+	return;
+}