missing overlay for I2S on radxa rock2a

[ralf33609]

Im using a radxa rock 2a sbc board with 40 Pin header.
I missed loadable I2S overlay.
I wanted to connect a I2S-DAC Max98357a to it and
already built myself a solution but dont know how to share. Pull request would exceed my expertise.

I am using the provided downloadable image thats provided with the armbian-imager.
uname -r
6.1.115-vendor-rk35xx

[ralf33609]

rk3528-i2s0-full-duplex.dts.txt

the attachment contains my working solution as user overlay for sbc radxa rock 2a that uses rockchip rk3528a