Schematic PDF of 8.97 MB named for the P20 lite; the name gives no brand or board number, but P20 lite is a Huawei model name. Diagrams like this help trace power rails from the PMIC, follow charging and display circuits, and identify parts around a shorted line when measuring. Any PDF reader opens it. As the file name carries no model code or board revision, compare the board markings and component layout of your phone with the drawings before relying on them.
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 .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.
Any PDF readerSumatraPDFFirefox / ChromeFlexBV (links PDF to boardview)