Schematic PDF covering the SM4375 chip, with an extra SM43 tag in the name that appears to repeat the family code; it is the same size, 1.57 MB, as another SM4375 file and may be a duplicate. No phone model is stated. Pages like these map the SoC pins, power domains and interfaces such as memory and display, helping trace a missing rail or locate a short near the processor. Compare with the other copy and verify against your board layout before use.
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.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)