The DSI doesn't care if you are using an adp7533 or not, which means that the panel configurations that are specific for the adp7533 can still be loaded even if the adp7533 is off.
Forget about the file the document points you to, that is a general file. You need to make your changes to apq8016-sbc.dtsi.
Notice at line 16 that it includes dsi-panel-jdi-1080p-video.dtsi.
If you look at that file, it is a panel configuration just like the two that are embedded in apq8016-sbc.dtsi.
oem_panel.c is part of littlekernel, NOT LINUX KERNEL.
littlekernel (LK) can feed a panel NAME to the linux kernel, or nothing at all.
You don't need valid output from LK to get valid output from Linux.
NOTHING you change in the linux kernel will have any impact on LK.
You have two choices for setting which panel configuration you want;
1) hard code it in the linux kernel. apq8016-sbc.dtsi:482
2) use the fastboot command I showed in the previous message to pass the desired panel name from LK to linux.
What you need to do:
1) set gpio 32 to hi to set the DSI output to the HS expansion port DSI pins.
2) write a panel configuration file for your panel.
3) include that panel configuration file in apq8016-sbc.dtsi
4) instruct the linux kernel on which panel configuration to use.
Perhaps to make that just a little more clear with respect to HOW it switches; in the most crude manner relating to things like cars and tractors, gpio 32 is like the power wire to a relay. When it is ON, the inputs on the relay connect electrically to one set of outputs. When it is OFF, the inputs on the relay connect electrically to the other set of outputs. Thus the DSI output pins on the SoC will be connected to the DSI pins on the HS IO port when gpio32 is HI (on) and those same output pins on the SoC will be connected to the adv7533 input pins when gpio32 is LOW (off).
The panel configuration, regardless of what it is named, is just the settings given to the DSI so that its output will match the panel's input. dsi_adv7533_1080p and dsi_adv7533_720p are just names for two possible DSI configurations. That they are loaded DOES NOT imply that the DSI signal is routed to the adv7533.