Disable SSC for Xavier NX PCIex4

We need to disable SCC for a PCIe camera, I found the following thread:
Tegra NX PCIe Reference Clock Design - Jetson & Embedded Systems / Jetson Xavier NX - NVIDIA Developer Forums

but could not find the dtsi file “tegra194-bpmp-p2888-uphy.dtsi” from Jetson SDK or kernel source.

Where can I find the dtsi file? Is there instructions of building the (bootloader?) dtb file?

I have built kernel Image and DTBs but not bootloader DTB.

Thanks in advance.