The code changes introduce the implementation of SBI serial output using the `IConsole` interface. This implementation includes support for both Legacy console API and Debug console API. The `LegacyConsole` and `DebugConsole` structs provide the specific implementations for each API, while the `UnionConsole` struct acts as a wrapper to support both APIs simultaneously. Additionally, the `println!` and `print!` macros are provided for convenient serial output.