Hello,
I too have a 8650 based laptop, in my case a Craig CLP281.
I have not been using the serial port in a while though it works and is not too hard to get to, I have just been using the console.
my wmt_scriptcmd has
====
display init force
mmcinit 0
textout -1 -1 \"Loading kernel...\" FFFFFF
fatload mmc 0 0 uzImage.bin
textout -1 -1 \"Starting Linux...\" FFFFFF
setenv bootargs 'mem=214M root=/dev/mmcblk0p2 noinitrd rw rootfstype=ext3 rootdelay=1 console=ttyWMT0,115200n8 console=ttyS0 console=tty0'
bootm 0
====
I don't remember which serial port I was using, but the video/keyboard was tty0
I think ttyS0 was for when I was running the original 2.6.32-? kernel and ttyWMT0 was for 4.14.14, though I am a bit fuzzy on that.
I built it on a plain
kernel.org 4.14.14 using
ARCH=arm CROSS_COMPILE=armv5tej-none-linux-gnueabi-
The arm-none-eabi may hit a problem, arm- should be able to compile armv5tej-, both agree on -none- as the manufacturer, I have OS -linux- though and -gnueabi- rather than -eabi- I have had issues sometimes with the gcc 4 part target tuples
I use the wm8650-mid.dtb as the device tree object.
If the kernel is booting the next worry would be insuring that the debian armel was compatible with armv5tej there are quite the stack of arm versions.
The part I have yet to figure out is how to enter the second usb controller in the device tree.
The first one works, I am not sure about hotplug it has been busy compiling gentoo xfce for the last week... 67cpu hours since Jan 30 for python:167 of 173 packages built. But still responsive over the console or ssh.
Enjoy,
Jim