Consider adding an `aliases` node to RISC-V DTB that includes `serial0` alias

Goal

Consider adding an aliases node to the DTB that has an entry that aliases serial0 to the serial@ device.

Technical details

When booting a RISCV system, qemu prepares a device tree blob describing its hardware configuration. On actual SoC, this DTB usually contains an alias for serial0. This is suggested for physical devices in the Linux kernel serial bindings documentation, where it says:

Each enabled UART may have an optional "serialN" alias in the "aliases" node,
where N is the port number (non-negative decimal integer) as printed on the
label next to the physical port.

Admittedly, Qemu does not have a physical port, but it would be nice to be able to write a kernel that boots on SoC by looking for serial0 and then finding Qemu's serial device.

Additional information

Example of an aliases section for physical SoC.