PDF schematic for the Xiaomi Redmi 9T, the name indicating that PCB layout pages accompany the circuit diagrams, file size about 2.33 MB. Having both lets a technician find a component on the board after reading its function on the circuit page. Typical uses are checking PMIC outputs, the charging path and connector pinouts, or locating a shorted capacitor. It opens in any PDF reader. Verify the handset's board version corresponds to the document before relying on positions.
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.