To define an N way split this define the following:
#define BOARD_HAS_MTD_PARTITION_OVERRIDE {"/fs/mtd_params", "/fs/mtd_waypoints","/fs/equal_part" }
OR
To define a percentage split this define the following:
#define BOARD_HAS_MTD_PARTITION_OVERRIDE {"/fs/mtd_params", "/fs/mtd_waypoints","/fs/tiny" }
#define BOARD_MTD_PARTITION_TABLE_SIZES {50.0f, 49.0f, 1.0f}