Hello,
At the moment, we see that Firmware (OpenWrt image) for LinkIt Smart can be upgraded by using 1.Web UI 2.From USB drive. Please refer the Linkit Smart 7688 Developers Guide.
The FOTA upgrades for ATMega32u4 is documented here. It must be possible to implement a similar feature by using your own cloud by writing your own upload script.
Thanks and Warm Regards.