diff --git a/MdeModulePkg/Include/Protocol/SdMmcOverride.h b/MdeModulePkg/Include/Protocol/SdMmcOverride.h
new file mode 100644
index 0000000000..0766252e56
--- /dev/null
+++ b/MdeModulePkg/Include/Protocol/SdMmcOverride.h
@@ -0,0 +1,97 @@
+/** @file
+  Protocol to describe overrides required to support non-standard SDHCI
+  implementations
+
+  Copyright (c) 2017 - 2018, Linaro, Ltd. All rights reserved.<BR>
+
+  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.
+
+**/
+
+#ifndef __SD_MMC_OVERRIDE_H__
+#define __SD_MMC_OVERRIDE_H__
+
+#include <Protocol/SdMmcPassThru.h>
+
+#define EDKII_SD_MMC_OVERRIDE_PROTOCOL_GUID \
+  { 0xeaf9e3c1, 0xc9cd, 0x46db, { 0xa5, 0xe5, 0x5a, 0x12, 0x4c, 0x83, 0x23, 0x23 } }
+
+#define EDKII_SD_MMC_OVERRIDE_PROTOCOL_VERSION    0x1
+
+typedef struct _EDKII_SD_MMC_OVERRIDE EDKII_SD_MMC_OVERRIDE;
+
+typedef enum {
+  EdkiiSdMmcResetPre,
+  EdkiiSdMmcResetPost,
+  EdkiiSdMmcInitHostPre,
+  EdkiiSdMmcInitHostPost,
+} EDKII_SD_MMC_PHASE_TYPE;
+
+/**
+
+  Override function for SDHCI capability bits
+
+  @param[in]      ControllerHandle      The EFI_HANDLE of the controller.
+  @param[in]      Slot                  The 0 based slot index.
+  @param[in,out]  SdMmcHcSlotCapability The SDHCI capability structure.
+
+  @retval EFI_SUCCESS           The override function completed successfully.
+  @retval EFI_NOT_FOUND         The specified controller or slot does not exist.
+  @retval EFI_INVALID_PARAMETER SdMmcHcSlotCapability is NULL
+
+**/
+typedef
+EFI_STATUS
+(EFIAPI * EDKII_SD_MMC_CAPABILITY) (
+  IN      EFI_HANDLE                      ControllerHandle,
+  IN      UINT8                           Slot,
+  IN  OUT VOID                            *SdMmcHcSlotCapability
+  );
+
+/**
+
+  Override function for SDHCI controller operations
+
+  @param[in]      ControllerHandle      The EFI_HANDLE of the controller.
+  @param[in]      Slot                  The 0 based slot index.
+  @param[in]      PhaseType             The type of operation and whether the
+                                        hook is invoked right before (pre) or
+                                        right after (post)
+
+  @retval EFI_SUCCESS           The override function completed successfully.
+  @retval EFI_NOT_FOUND         The specified controller or slot does not exist.
+  @retval EFI_INVALID_PARAMETER PhaseType is invalid
+
+**/
+typedef
+EFI_STATUS
+(EFIAPI * EDKII_SD_MMC_NOTIFY_PHASE) (
+  IN      EFI_HANDLE                      ControllerHandle,
+  IN      UINT8                           Slot,
+  IN      EDKII_SD_MMC_PHASE_TYPE         PhaseType
+  );
+
+struct _EDKII_SD_MMC_OVERRIDE {
+  //
+  // Protocol version of this implementation
+  //
+  UINTN                         Version;
+  //
+  // Callback to override SD/MMC host controller capability bits
+  //
+  EDKII_SD_MMC_CAPABILITY       Capability;
+  //
+  // Callback to invoke SD/MMC override hooks
+  //
+  EDKII_SD_MMC_NOTIFY_PHASE     NotifyPhase;
+};
+
+extern EFI_GUID gEdkiiSdMmcOverrideProtocolGuid;
+
+#endif
diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 0298bed6e3..61d034fba8 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -562,6 +562,9 @@
   ## Include/Protocol/SmmMemoryAttribute.h
   gEdkiiSmmMemoryAttributeProtocolGuid = { 0x69b792ea, 0x39ce, 0x402d, { 0xa2, 0xa6, 0xf7, 0x21, 0xde, 0x35, 0x1d, 0xfe } }
 
+  ## Include/Protocol/SdMmcOverride.h
+  gEdkiiSdMmcOverrideProtocolGuid = { 0xeaf9e3c1, 0xc9cd, 0x46db, { 0xa5, 0xe5, 0x5a, 0x12, 0x4c, 0x83, 0x23, 0x23 } }
+
 #
 # [Error.gEfiMdeModulePkgTokenSpaceGuid]
 #   0x80000001 | Invalid value provided.