Hi,
For the LPC55S69-EVK pin name, as you know that the Port pin is unique and map to only one pin. For example, for the pin 1 of P17, it is FC4_I2C_SCL_ARD, you can search on the schematics with pdf format,
xiangjun_rong_0-1730770526888.png
By searching the key word "FC4_I2C_SCL_ARD", you can see that the the node corresponds PIO1_20 or pin 4 of LPC5569.
You can configure the PIO1_20 as FC4_I2C_SCLK, it is okay.
xiangjun_rong_1-1730770852613.png
From hardware register configuration, each GPIO pin corresponds to a IOCON register, you can set up the FUNC bit to determine the pin function.
xiangjun_rong_2-1730771311190.png
There is not doc which describes the map between the signal name and pin map for the EVK board.
Hope it can help you
BR
XiangJun Rong