arm: socfpga: soc64: Add SMC helper function for Intel SOCFPGA (64bits)

invoke_smc() allow U-Boot proper running in non-secure mode (EL2)
to invoke SMC call to ATF's PSCI runtime services such as
System Manager's registers access, 2nd phase bitstream FPGA
reconfiguration, Remote System Update (RSU) and etc.

smc_send_mailbox() is a send mailbox command helper function which invokes
the ATF's PSCI runtime service (function ID: INTEL_SIP_SMC_MBOX_SEND_CMD)
to send mailbox messages to Secure Device Manager (SDM).

Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
diff --git a/arch/arm/mach-socfpga/include/mach/smc_api.h b/arch/arm/mach-socfpga/include/mach/smc_api.h
new file mode 100644
index 0000000..bbefdd8
--- /dev/null
+++ b/arch/arm/mach-socfpga/include/mach/smc_api.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2020 Intel Corporation
+ */
+
+#ifndef _SMC_API_H_
+#define _SMC_API_H_
+
+int invoke_smc(u32 func_id, u64 *args, int arg_len, u64 *ret_arg, int ret_len);
+int smc_send_mailbox(u32 cmd, u32 len, u32 *arg, u8 urgent, u32 *resp_buf_len,
+		     u32 *resp_buf);
+
+#endif /* _SMC_API_H_ */