RAR archive of 5.48 MB named only SM, which gives no model, board number or file type. The prefix resembles Samsung model codes, but the actual device cannot be confirmed from the name, so the contents must be opened and checked. If it holds schematics or service documents, match the model code and board revision on the device before use. If it contains firmware, verify the target and make a backup before flashing anything.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @uzb4422. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
7-ZipWinRARThe Unarchiver (macOS)