How to use the serial port on the R64 GPIO?

Banana Pi BPI-R4/BPI-R3 Mini/BPI-R3/BPI-R64/BPI-R2
1

I see there are four serial ports on R64 GPIO, TXD1/RXD1~TXD4/RXD4, how to use them as serial port or RS232?

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2

They are already defined in dtsi

https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/mediatek/mt7622.dtsi#L384

You have to enable them in bpi-r64.dts. when booting serial driver should catch them if gpio not blocked by another function