Enable UART4 in AM335x

Hello 

       We are designing custom device with AM335x. We need to connect serial device with AM335x processor over UART4. 

UART4 details:-

BALL                  Name

E18                  Uart4_rxd_mux1  (Mode-1)

E17                 Uart4_txd_mux1    (Mode-1)

I tried to enable UART4 in board file but there is no muxing details for UART4 in mux33xx.c, details are,

_AM33XX_MUXENTRY(UART0_CTSN, 0,
                                     "uart0_ctsn", NULL, "d_can1_tx", "i2c1_sda",
                                     "spi1_d0", NULL, NULL, "gpio1_8"),

_AM33XX_MUXENTRY(UART0_RTSN, 0,
                                      "uart0_rtsn", NULL, "d_can1_rx", "i2c1_scl",
                                      "spi1_d1", "spi1_cs0", NULL, "gpio1_9"),

Here no detail for uart4_rx in mode1, here its defined as NULL. 

How to add the entry for UART4 in mux33xx.c ?

And another is question, /dev/ttyO4 configured for T17, U17 ball or it can be modify to E18 & E17 ?