Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/30027 )
Change subject: Documentation/mainboard/lenovo/t420.md: add pic of chip ......................................................................
Patch Set 1: Code-Review+1
IMHO, it's worth to mention that GND is connected to various points such as mounting holes and connector shells. That way, to know where GND is on the chip, one could just measure the resistance from the pins to GND with an ohmeter. The correct pin would show minimal resistance.
Other than that, and what Patrick mentioned, this looks good to me. (other than my OCD complaining about how dirty the mainboard is :P)