R24.2 to R28.1 migration

R28 is profoundly different from R24. Is there a doc that explains how to migrate between the systems? I particular I’m having a hard time porting over my device specification from kernel 3.x to 4.4. What happened to the device tree source (dts) for tegra210? the all disappeared! Also the extlinux.conf does not choose anymore the drb, and a myriad of other small differences. The installation guide makes no reference to the device tree (did I miss it?)
How should I manage to port the customizations I have in the device tree, gpio config, etc, to the new 4.4 kernel?

The R28 kernel source actually comes with “source/kernel/”, “source/hardware/”, and a couple of other subdirectories. You’ll find dts files in the “hardware/nvidia/platform/t210/”. There are some dts files in the u-boot directory as well.

Probably much of the rearrangement is due to this being the first L4T release to support both the X1 and X2. It seems that some of the actual loading of device tree migrated into U-Boot for this reason as well.

Attaching an extracted DTS for reference (it is from a default R28.1 TX1 install using dtc on the “/proc/device-tree” directory).
extracted_tx1-4.4.38-tegra.txt.gz (62.5 KB)