moby: define the i2s bus

this is enough for the sound card to come online, visible in /dev/snd and also pipewire

however i don't *hear* anything. speaker-test -c 2 does not work

hosts/modules/hal/pine64-pinephone-pro/rk3399-pinephone-pro-sound.dtso

@@ -63,6 +63,8 @@
 //   other RK3399 device with audio configured
 // - <Documentation/devicetree/bindings/mfd/rockchip,rk818.yaml>
 //   regulator definition
+// - <Documentation/devicetree/bindings/sound/rockchip-i2s.yaml>
+//   I2S audio definition
 
 // for symbols like SCLK_I2S_8CH_OUT
 #include <dt-bindings/clock/rk3399-cru.h>
@@ -200,5 +202,19 @@
         };
 };
 
-// TODO: define `/i2s0` node, for the actual audio data
+// defined (as disabled) in rk3399-base.dtsi:
+// - i2s0: i2s@ff880000
+//     compatible = "rockchip,rk3399-i2s", "rockchip,rk3066-i2s"
+&i2s0 {
+        rockchip,playback-channels = <2>;
+        // builtin mic on IN1, headphone mic on IN2
+        rockchip,capture-channels = <2>;
+        // i2s0_2ch_bus is [RK3399]PD0,PD1,PD2,PD3,PD7,PA0
+        //   maps to I2S0_SCLK,I2S0_LRCK_RX,I2S0_LRCK_TX,I2S0_SDI0,I2S0_SDO0,I2S_CLK
+        // 8ch_bus adds PD4,PD5,PD6
+        //   maps to NC,NC,TP8
+        pinctrl-0 = <&i2s0_2ch_bus>;
+        status = "okay";
+};
+
 // TODO: what are `io_domains`?