Understand SOM number , SOM model , carrier board and ref board

[BSP_User]

Hi,
I wanted to verify the distinguish between the following model numbers:

1. P3668-0000/P3668-0001/P3668-0002 → they all represent a Jetson Xavier NX SOM
2. P3509-0000 → represents a carrier board (for example the one that comes with the NX devkit)
3. T194 → ?
   I read it is a model number of a xavier nx. what is the relation between T194 and P3668-0000?
   T194 = Xavier NX in general and P3668-0000 = specific Xavier NX?
4. target_board = “t186ref” → ?
   I saw this in the p3668.conf.common
   from my understanding the t186 is older than the T194 so why they use it?

p.s
what is jakku in the t19x platform? is it a name of a specific xavier nx SOM? and where I choose which .dts files to compile? (the ones from jakku from mccoy or others?)
I know that we write the final dtb file in the board.conf but I don’t know at which stage exactly the dtb is built and where I specify the specific .dts files that I want to use)

thanks

[kayccc]

Please check the Jetson Modules and Configurations
with Respective Jetson Developer Kit Carrier Board table at NVIDIA Jetson Linux Developer Guide : Quick Start | NVIDIA Docs