diff --git a/plat/intel/soc/common/include/socfpga_mailbox.h b/plat/intel/soc/common/include/socfpga_mailbox.h
index 90b1fa6..1f4b2a4 100644
--- a/plat/intel/soc/common/include/socfpga_mailbox.h
+++ b/plat/intel/soc/common/include/socfpga_mailbox.h
@@ -113,6 +113,7 @@
 #define MBOX_WORD_BYTE					4U
 #define MBOX_RESP_BUFFER_SIZE				16
 #define MBOX_CMD_BUFFER_SIZE				32
+#define MBOX_INC_HEADER_MAX_WORD_SIZE			1024U
 
 /* Execution states for HPS_STAGE_NOTIFY */
 #define HPS_EXECUTION_STATE_FSBL			0
@@ -213,6 +214,8 @@
 			unsigned int *resp_len);
 int mailbox_send_cmd_async(uint32_t *job_id, uint32_t cmd, uint32_t *args,
 			unsigned int len, unsigned int indirect);
+int mailbox_send_cmd_async_ext(uint32_t header_cmd, uint32_t *args,
+			unsigned int len);
 int mailbox_read_response(uint32_t *job_id, uint32_t *response,
 			unsigned int *resp_len);
 int mailbox_read_response_async(uint32_t *job_id, uint32_t *header,
diff --git a/plat/intel/soc/common/include/socfpga_sip_svc.h b/plat/intel/soc/common/include/socfpga_sip_svc.h
index cc44db5..b1be6a6 100644
--- a/plat/intel/soc/common/include/socfpga_sip_svc.h
+++ b/plat/intel/soc/common/include/socfpga_sip_svc.h
@@ -24,6 +24,14 @@
 #define INTEL_SIP_SMC_CMD_V2_RANGE_BEGIN			0x400
 #define INTEL_SIP_SMC_CMD_V2_RANGE_END				0x4FF
 
+/* SiP V2 protocol header */
+#define INTEL_SIP_SMC_HEADER_JOB_ID_MASK			0xF
+#define INTEL_SIP_SMC_HEADER_JOB_ID_OFFSET			0U
+#define INTEL_SIP_SMC_HEADER_CID_MASK				0xF
+#define INTEL_SIP_SMC_HEADER_CID_OFFSET				4U
+#define INTEL_SIP_SMC_HEADER_VERSION_MASK			0xF
+#define INTEL_SIP_SMC_HEADER_VERSION_OFFSET			60U
+
 /* SMC SiP service function identifier for version 1 */
 
 /* FPGA Reconfig */
@@ -143,6 +151,10 @@
 #define INTEL_SIP_SMC_V2_REG_UPDATE				0xC2000403
 #define INTEL_SIP_SMC_V2_HPS_SET_BRIDGES			0xC2000404
 
+/* V2: Mailbox function identifier */
+#define INTEL_SIP_SMC_V2_MAILBOX_SEND_COMMAND			0xC2000420
+#define INTEL_SIP_SMC_V2_MAILBOX_POLL_RESPONSE			0xC2000421
+
 /* SMC function IDs for SiP Service queries */
 #define SIP_SVC_CALL_COUNT					0x8200ff00
 #define SIP_SVC_UID						0x8200ff01