Xiaomi Redmi Note 9S smartphone schematic, a 2.04 MB PDF. It is meant for board-level work such as tracing the charging circuit, checking PMIC rails, following USB and battery connector lines, and finding the sources of shorts on the main supply. The document can be opened with any PDF reader, and searching net labels shortens the time spent hunting a signal across pages. For physical component positions it is worth combining with a boardview, and the phone model should be verified against the schematic first.
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 @mischematic. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.