current bsp only uses tpm4 as pwm, for tpm3, maybe you can try this
tpm3: pwm@424e0000 {
compatible = "fsl,imx7ulp-pwm";
reg = <0x424e0000 0x1000>;
clocks = <&clk IMX93_CLK_TPM3_GATE>;
assigned-clock-parents = <&clk IMX93_CLK_24M>;
ssigned-clock-rates = <24000000>;+
#pwm-cells = <3>;
status = "disabled";
};