qmk-firmware/quantum/template/template.c

#include "%KEYBOARD%.h"

__attribute__ ((weak))
void matrix_init_user(void) {
	// leave these blank
}

__attribute__ ((weak))
void matrix_scan_user(void) {
	// leave these blank
}

void matrix_init_kb(void) {
	// put your keyboard start-up code here
	// runs once when the firmware starts up
	matrix_init_user();
}

void matrix_scan_kb(void) {
	// put your looping keyboard code here
	// runs every cycle (a lot)
	matrix_scan_user();
}