In IMX7D Sabre development board, there is 1GB ram available. How can I reserve some portion of ram((I need min 10Mb) and map it into userspace in linux ? I have seen that there is "linux,usable-memory" property in dts to mention the memory used by linux. Using that may be I can reserve last 10mb, but how can I map and use it in userspace ? Can mmap works in this case also ?