So on DB410C we don’t have an end to end example, mostly because the SoC in DB410C is not configured with any secure keys (and also because its a developer board and it would inconvenient to have signed kernels). However there is information in the release notes on how to build a signed LittleKernel (scroll down):
Basically the DB410C is configured to require that a signature block exists but it will not validate it. The purpose of this is to make the flow into LK the same for both non-secure devices like DB410C and secure devices with private keys making it easier to reuse the components from DB410C on similar boards.
However, once you have a signed LK everything should end up “the same as Android” since we use the same abootimg format for debian and Android kernels. Thus, if you able to source a SoC with private keys installed you should also be able to access information from Qualcomm on how Android kernels are signed.