The 4376051 PEARL 4.0 is variously labelled a “power” and “connector” IC on various sources. There’s also this repair hint that shows in involved with SIM interfacing. Confusingly PEARL was one of the Symbian design reference platforms that became the basis of Nokia’s Symbian offerings, but as the X3-00 was a (non-Symbian) Series 40 phone, that’s a red herring. I’d guess this is actually the CPU/microcontroller for the phone, and probably a custom Nokia part.
The chip towards the bottom left with the label “CSR” at the top is probably bluetooth and/or FM radio- CSR was a company called “Cambridge Silicon Radio” that is now part of Qualcomm and used to do lots of bluetooth and RF stuff.
The right of that the Skyworks SKY77527 is a Tx front end module for quad band GSM/EDGE - see https://www.skyworksinc.com/en/Products/Front-end-Modules/SKY77527 for more info.
The small TI 3280 is a low power RF DC-DC convertor chip - see https://www.ti.com/lit/ds/symlink/lm3280.pdf?ts=1588799142598 for the data sheet for that one.
The Samsung K5W1G12 chip is most likely the flash memory - I couldn’t find that particular one but there’s lots in that series that are NAND or NOR logic memory in the 32-64MB range, which sounds about right for this generation of phone.
The little AAD package in the top right is probably some sort of display driver/controller. I couldn’t find that nor the ST MIcroelectronics components surrounding it in the grey packages.
You might find this X3 manual handy too.
Hope that help.