AM3358 evm Uart not working

Please make sure that you have modified the CONTROL MODULE for UART1 (i.e PINMUXing) ?
You can read the following OFFSET with CONTROL module base address and confirm.

980h conf_uart1_rxd
984h conf_uart1_txd

Something like this.

uart1: serial@48022000 {
pinctrl-names = "default";
pinctrl-0 = <&uart1_pins>;

status = "okay";
};

and
uart1_pins: pinmux_uart1_pins {
pinctrl-single,pins = <
0x180 (PIN_INPUT_PULLUP | MUX_MODE0) /* uart1_rxd.uart1_rxd */
0x184 (PIN_OUTPUT_PULLDOWN | MUX_MODE0) /* uart1_txd.uart1_txd */
>;
};

The pinmux files are given for reference. You can't directly reuse them.

You can't use the generated mux.h directly in your project. You should trim the needed parts and place them in the appropriate functions/nodes.

For example if you generate devicetree.txt with this content below, you can't just replace the old dts with this one. You should copy the needed lines and place them in proper locations and modify the device's dts respectively. Here you can find information about device tree design www.devicetree.org/Device_Tree_Usage

/* This file was auto-generated by TI PinMux on 2/25/2016 at 1:38:00 PM. */
/* This file should only be used as a reference. Some pins/peripherals, */
/* depending on your use case, may need additional configuration. */


myuart1_pins_default: myuart1_pins_default {
pinctrl-single,pins = <
0x180 ( PIN_INPUT | MUX_MODE0 ) /* (D16) uart1_rxd.uart1_rxd */
0x184 ( PIN_OUTPUT | MUX_MODE0 ) /* (D15) uart1_txd.uart1_txd */
0x178 ( PIN_INPUT | MUX_MODE0 ) /* (D18) uart1_ctsn.uart1_ctsn */
0x17c ( PIN_INPUT | MUX_MODE0 ) /* (D17) uart1_rtsn.uart1_rtsn */
0x12c ( PIN_INPUT | MUX_MODE5 ) /* (K18) gmii1_txclk.uart1_dcdn */
0x130 ( PIN_INPUT | MUX_MODE5 ) /* (L18) gmii1_rxclk.uart1_dsrn */
0x134 ( PIN_INPUT | MUX_MODE5 ) /* (L17) gmii1_rxd3.uart1_dtrn */
0x138 ( PIN_INPUT | MUX_MODE5 ) /* (L16) gmii1_rxd2.uart1_rin */
>;
};

/* Optional sleep pin settings. Must manually enter values in the below skeleton. */
myuart1_pins_sleep: myuart1_pins_sleep {
pinctrl-single,pins = <
0x180 ( ) /* (D16) uart1_rxd.uart1_rxd */
0x184 ( ) /* (D15) uart1_txd.uart1_txd */
0x178 ( ) /* (D18) uart1_ctsn.uart1_ctsn */
0x17c ( ) /* (D17) uart1_rtsn.uart1_rtsn */
0x12c ( ) /* (K18) gmii1_txclk.uart1_dcdn */
0x130 ( ) /* (L18) gmii1_rxclk.uart1_dsrn */
0x134 ( ) /* (L17) gmii1_rxd3.uart1_dtrn */
0x138 ( ) /* (L16) gmii1_rxd2.uart1_rin */
>;
};