Serial console is what I would consider “important backup” in embedded. However, if you remove the right part of the kernel boot argument, then this tty will stop being used for console and messages once Linux starts. On the other hand, if this port sees any activity at all during boot within the U-Boot stage, then your system will halt. You’d need to have any hardware removed from this port until after boot completes.
For more recent releases the kernel command line boot arguments are in the device tree, and the device tree is flashed to a partition after being signed. Thus simple steps of updating a file and copying it in no longer apply.
Within the device tree look for “chosen”. This will have a node within it, “bootargs”. A kernel accepts two consoles as arguments…you’d be removing the arguments related to serial console. Those arguments look like:
console=ttyS0,115200n8
Eliminate those from your device tree, and then flash the new device tree. Serial console should then be removed after U-Boot is gone (you would have to modify U-Boot to get rid of it there).
J17 is probably looking nicer :P