ArmPkg: Introduce SCMI protocol

This change introduces a new SCMI protocol driver for
Arm systems. The driver currently supports only clock
and performance management protocols. Other protocols
will be added as and when needed.

Clock management protocol is used to configure various clocks
available on the platform e.g. HDLCD clock on the Juno platforms.

Whereas performance management protocol allows adjustment
of various performance domains. Currently this is used to evaluate
performance of the Juno platform.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Girish Pathak <girish.pathak@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

ArmPkg/Drivers/ArmScmiDxe/ScmiDxe.h

@@ -0,0 +1,41 @@
+/** @file
+
+  Copyright (c) 2017-2018, Arm Limited. All rights reserved.
+
+  This program and the accompanying materials
+  are licensed and made available under the terms and conditions of the BSD License
+  which accompanies this distribution.  The full text of the license may be found at
+  http://opensource.org/licenses/bsd-license.php
+
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
+
+  System Control and Management Interface V1.0
+    http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/
+    DEN0056A_System_Control_and_Management_Interface.pdf
+**/
+#ifndef SCMI_DXE_H_
+#define SCMI_DXE_H_
+
+#define MAX_PROTOCOLS        6
+#define PROTOCOL_ID_MASK     0xF
+#define MAX_VENDOR_LEN       SCMI_MAX_STR_LEN
+
+/** Pointer to protocol initialization function.
+
+  @param[in]  Handle  A pointer to the EFI_HANDLE on which the protocol
+                      interface is to be installed.
+
+  @retval EFI_SUCCESS  Protocol interface installed successfully.
+**/
+typedef
+EFI_STATUS
+(EFIAPI *SCMI_PROTOCOL_INIT_FXN)(
+  IN  EFI_HANDLE  *Handle
+  );
+
+typedef struct {
+  SCMI_PROTOCOL_INIT_FXN Init;
+} SCMI_PROTOCOL_INIT_TABLE;
+
+#endif /* SCMI_DXE_H_ */