In addition to the Android source, you will need the kernel source for your device, and some vendor specific (mostly not open source) files and libraries. If these are not provided by the vendor it will be next to impossible to build. Finally you need to make all these things build and run properly.thanks , for the info , i understand the hardware restrictions , but in case if still some one wanna see if its possible so what should i be looking for , asop for android 5 or 6 , ? ( suppose for any other device ? )
actually i wanna understand that if i have phone which is not supported by google latest versions NO OTA or upgrade , so what could be option be if i wana start my own rom custom one what is must have for starting rom for any device ( latest android )