Summary
What makes Linux so powerful is the ability to configure the kernel however we need to. The definitive place to get the kernel source code is https://www.kernel.org/, but you will probably need to get the source for a particular SoC or board from the vendor of that device or a third party that supports that device. The customization of the kernel for a particular target may consist of changes to the core kernel code, additional drivers for devices that are not in mainline Linux, a default kernel configuration file, and a device tree source file.
Normally, you start with the default configuration for your target board and then tweak it by running one of the configuration tools such as menuconfig. One of the things you should consider at this point is whether the kernel features and drivers should be disabled, compiled as modules, or built-in. Kernel modules are usually no great advantage for embedded systems where the feature set and hardware are usually well defined. However...
