How to build img firmware for IoT devices?

Question

ARM

Good day!
I will warn you in advance that I am a lamer on this topic, the area of ​​\u200b\u200bmy professional knowledge is not here at all, therefore, to knowledgeable people, something that I will say may seem like nonsense.
I have a board running an arm processor AM355X. The board also has usb, ethernet, etc. In fact, it is a small computer. I am writing software for it that communicates via the CAN bus with some other devices. I found that many modules that I need do not work - modpobe can, vcan, etc. gives an exec error.
I decided to rebuild the kernel, downloaded the sources, compiled, copied the necessary modules manually to the device, no longer crash when connected (although I did not check the performance).
It is planned to release serial devices on which there will be a firmware with my software. I managed to assemble the core itself, but the core is not a full-fledged firmware. And I would like to have a full-fledged firmware and even an img image. Accordingly, how to check it?
Thanks in advance.