I have an Uputronics GPS "HAT" on my RPi3 running a GENERIC64 build of 8.99.28.
I got gpiopps and everything working, the last piece is the actual NMEA/U-Blox data feed. I believe I have two particular problems:
1) I can't seem to figure out how to get the kernel to use the HDMI/wsdisplay/wscons as the system console instead of com0. I've tried tinkering with /etc/ttys & /etc/wscons.conf and nothing. /boot/cmdline.txt already has "console=fb".
2) I have a feeling that the system is using the default of mapping GPIO 14/15 to the BCM AUX UART instead of the ARM PL011 UART. Since overlays don't seem to work, do I need to modify /boot/bcm2837-rpi-3-b.dtb to accomplish this? I'm assuming so. If so, that part I've done before.