it’s correct that you should refer to tegra194-gpio.h for Xavier’s GPIO definition.
i.e. #define TEGRA194_AON_GPIO_PORT_BB 1
you may check kernel messages for the AON-GPIO allocation range, it’s starting from 248.
i.e. [ 0.882955] gpiochip_setup_dev: registered GPIOs 248 to 287 on device: gpiochip1 (tegra-gpio-aon)
so,
let me correct my previous comments, this pin GPIO3_PBB.00, GPIO number = 1*8+248 = 256.