Add Xilinx ZynqMP IPI mailbox service

Add IPI mailbox service to manage Xilinx ZynqMP IPI(Inter Processors
Interrupt) access.

Signed-off-by: Wendy Liang <jliang@xilinx.com>
diff --git a/plat/xilinx/zynqmp/ipi_mailbox_service/ipi_mailbox_svc.h b/plat/xilinx/zynqmp/ipi_mailbox_service/ipi_mailbox_svc.h
new file mode 100644
index 0000000..387ffd2
--- /dev/null
+++ b/plat/xilinx/zynqmp/ipi_mailbox_service/ipi_mailbox_svc.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+/* ZynqMP IPI mailbox doorbell service enums and defines */
+
+#ifndef _IPI_MAILBOX_SVC_H_
+#define _IPI_MAILBOX_SVC_H_
+
+#include <stdint.h>
+
+/*********************************************************************
+ * Enum definitions
+ ********************************************************************/
+
+/* IPI SMC function numbers enum definition */
+enum ipi_api_id {
+	/* IPI mailbox operations functions: */
+	IPI_MAILBOX_OPEN = 0x1000,
+	IPI_MAILBOX_RELEASE,
+	IPI_MAILBOX_STATUS_ENQUIRY,
+	IPI_MAILBOX_NOTIFY,
+	IPI_MAILBOX_ACK,
+	IPI_MAILBOX_ENABLE_IRQ,
+	IPI_MAILBOX_DISABLE_IRQ
+};
+
+/*********************************************************************
+ * IPI mailbox service APIs declarations
+ ********************************************************************/
+
+/* IPI SMC handler */
+uint64_t ipi_smc_handler(uint32_t smc_fid, uint64_t x1, uint64_t x2,
+			 uint64_t x3, uint64_t x4, void *cookie, void *handle,
+			 uint64_t flags);
+
+#endif /* _IPI_MAILBOX_SVC_H_ */