This is an import of the reworked LEDE dts files. Besides other things they make it easier for us to reuse.
The only diffs left are for the following SoCs:
MT7620A (fbsd-mt7620a.dtsi)
MT7621 (fbsd-mt7621.dtsi)
MT7628 (fbsd-mt7628an.dtsi)
RT3883 (fbsd-rt3883.dtsi)
So we include the fbsd-*.dtsi files at the end of the original LEDE dtsi files, using '#include "fbsd-xxxx.dtsi"'.
For example, for MT7621, the LEDE dtsi file is mt7621.dtsi. At the end of it we add:
#include "fbsd-mt7621.dtsi"