arm64: dts: rockchip: Add SPDIF nodes to RK3576 device tree

arm64: dts: rockchip: Add SPDIF nodes to RK3576 device tree

Add support for all six SPDIF transmitters found in the RK3576.
The nodes have been taken over from the BSP kernel and checked
against the TRM (power domain descriptions from chapter 6.3.2,
addresses from "Table 1-1 Address Mapping", interrupt from
"Table 1-3 RK3576 Interrupt Connection List" (TRM numbers are
off by 32 due to SGI/PPI not being numbered separately). The
TRM lacks a proper clock tree, but fortunately are quite obvious
for the SPDIF IP.

Note, that the RK3576 also has 3 SPDIF receivers, which need their
own binding and are not handled in this patch.

A typical use case for the SPDIF transmitters is audio support for
the Displayport (DP) controller. DP requires inserting PCUV control
bits, which requires software support when using I2S. The SPDIF IP
can add it automatically and thus is preferred.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://patch.msgid.link/20260316-rk3576-spdif-v1-2-acb75088b560@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>