Newbie: building l4t from source, which branch/tag?

I haven’t compiled Linux in years, so please be patient.

I want to build a custom image (ultimately so I can add WiFi / Bluetooth - seriously, who uses Ethernet?).

I assume I need to:
a) checkout the l4t branch (mainline stable does not yet support Jetson? Yocto does not support Jetson?)
b) download the sample filesys and place it somewhere
c) download the custom Nvidia drivers and place them somewhere
d) make menuconfig, tweak, build
e) create a bootable SD card w/ UBoot / zImage / etc.

For step a) I thought I cloned the latest l4t, but I see no Jetson BSP and the kernel is 2.6?

Git tells me:

origin git:// (fetch)
origin git:// (push)
On branch tegra-l4t-r19.3

But there is no arch/arm/mach-tegra, and the Makefile shows:

NAME=Woozy Numbat

What am I missing?

Many thanks,

Hmm, looks like I missed a git warning about “ambiguous refname” when I checked out the repo:

cooper@tesla-linux:/code/tegra/linux-l4t$ git checkout tegra-l4t-r19.3
warning: refname ‘tegra-l4t-r19.3’ is ambiguous.
Switched to branch ‘tegra-l4t-r19.3’

The correct checkout command is:

cooper@tesla-linux:/code/tegra/linux-l4t$ git checkout l4t/l4t-r19.3
Checking out files: 100% (54338/54338), done.
Branch l4t/l4t-r19.3 set up to track remote branch l4t/l4t-r19.3 from origin.
Switched to a new branch ‘l4t/l4t-r19.3’

Now I see the code I expect.