EmbeddedPkg/Drivers: add virtual keyboard driver

This driver is used to simulate a keyboard. For example, user
could read GPIO setting or data from RAM address. If the value
matches the expected pattern, it could trigger a key pressed
event.

User needs to implement hooks of PLATFORM_VIRTUAL_KBD_PROTOCOL.
There're 4 hooks in this protocol.
Register(): Quote the interface that user needs. For example, user
needs to locate GPIO protocol if he wants to simulate a GPIO value
as a key.
Reset(): Do the initialization before reading value.
Query(): Read value. If the value matches the expected pattern,
trigger a key pressed event.
Clear(): Clean the value if necessary.

Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>

EmbeddedPkg/Drivers/VirtualKeyboardDxe/VirtualKeyboardDxe.inf

@@ -0,0 +1,60 @@
+## @file
+# Virtual Keyboard driver.
+#
+# Copyright (c) 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.
+#
+##
+
+[Defines]
+  INF_VERSION                    = 0x00010019
+  BASE_NAME                      = VirtualKeyboardDxe
+  FILE_GUID                      = 88079b18-b42b-44aa-a6f2-b83911075e89
+  MODULE_TYPE                    = UEFI_DRIVER
+  VERSION_STRING                 = 1.0
+  ENTRY_POINT                    = InitializeVirtualKeyboard
+
+#
+# The following information is for reference only and not required by the build tools.
+#
+#  VALID_ARCHITECTURES           = IA32 X64 IPF ARM AARCH64
+#
+#  DRIVER_BINDING                = gVirtualKeyboardDriverBinding
+#  COMPONENT_NAME                = gVirtualKeyboardComponentName
+#
+
+[Sources.common]
+  ComponentName.c
+  VirtualKeyboard.c
+
+[Packages]
+  EmbeddedPkg/EmbeddedPkg.dec
+  MdeModulePkg/MdeModulePkg.dec
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  BaseLib
+  BaseMemoryLib
+  DebugLib
+  IoLib
+  ReportStatusCodeLib
+  UefiBootServicesTableLib
+  UefiDriverEntryPoint
+  UefiLib
+
+[Protocols]
+  gEfiDriverBindingProtocolGuid
+  gEfiSimpleTextInProtocolGuid
+  gEfiSimpleTextInputExProtocolGuid
+  gPlatformVirtualKeyboardProtocolGuid
+
+[Depex]
+  TRUE