initial PR for SDIOBlockdevice implementation

CMakeLists.txt

@@ -0,0 +1,40 @@
+
+add_library(mbed-storage-sdio STATIC)
+
+list(APPEND SOURCEFILES 
+    SDIOBlockDevice.cpp
+)
+
+target_include_directories(mbed-storage-sdio INTERFACE .)
+
+if("STM32F4" IN_LIST MBED_TARGET_LABELS)
+    target_include_directories(mbed-storage-sdio PUBLIC ./TARGET_STM/TARGET_STM32F4)
+    list(APPEND SOURCEFILES
+        TARGET_STM/TARGET_STM32F4/sdio_device.c
+    )
+endif()
+
+if("STM32F7" IN_LIST MBED_TARGET_LABELS)
+    target_include_directories(mbed-storage-sdio PUBLIC ./TARGET_STM/TARGET_STM32F7)
+    list(APPEND SOURCEFILES
+        TARGET_STM/TARGET_STM32F7/sdio_device.c
+    )
+endif()
+
+if("STM32H7" IN_LIST MBED_TARGET_LABELS)
+    target_include_directories(mbed-storage-sdio PUBLIC ./TARGET_STM/TARGET_STM32H7)
+    list(APPEND SOURCEFILES
+        TARGET_STM/TARGET_STM32H7/sdio_device.c
+    )
+endif()
+
+target_link_libraries(mbed-storage-sdio
+    PUBLIC
+        mbed-rtos-flags
+        mbed-storage-blockdevice
+    )
+
+target_sources(mbed-storage-sdio
+    PRIVATE
+        ${SOURCEFILES}
+    )

README.md

@@ -7,3 +7,25 @@ This is not officially supported driver.
 ## License & Contributions 
 
 The software is provided under [Apache-2.0 license](LICENSE). Contributions to this project are accepted under the same license. Please see [contributing.md](CONTRIBUTING.md) for more info.
+
+This is an implementation for a blockdevice to use SDHC cards via SDIO interface.
+
+## Supported Hardware
+- STM32F4
+- STM32F7
+
+## Tested Hardware
+- STM Discovery board 32F469IDISCOVERY, Targetname: DISCO_F469NI
+  https://os.mbed.com/platforms/ST-Discovery-F469NI/
+- STM Discovery board 32F746IDISCOVERY, Targetname: DISCO_F746NG
+  https://os.mbed.com/platforms/ST-Discovery-F746NG/
+
+
+## Driver Description
+This SDIOBlockdevice inherits from Blockdevice. The implementation uses an intermediate layer for the target specific code. This version uses the STM HAL 
+for the SD card communication, an approach that is not fully mBed compliant. So this driver is not part of the mbed-os, a cleaner solution maybe supplied in the future. Anyway, this driver passes the same tests as for a SDBlockdevice with SPI interface.
+
+## Usage
+The driver is used like other blockdevices, a good starting point is https://github.com/ARMmbed/mbed-os-example-filesystem
+
+