This article will stand on high level to scan initialization modules.

User press power key ……

First, Boot ROM
　- Loads the BootLoader into RAM and starts executing.

Second, BootLoader
　- Start up and find the system kernel.
　- Bootloader is a place where manufacturers put their locks
　　and restrictions.
　- Detects external RAM
　- Setups the network, memory … etc, which requires to run Kernel.

Third, Kernel
　- Setup cache
　　Protected memory
　　Scheduling
　　Loads drivers
　　Starts kernel daemons
　　Mounts root file system
　　Initializing Input/Output
　　Starts interrupts
　　Initializes process table ……
　- Looks for “init” in system files
　- Launch root process

Forth, Init (user space)
　- Mounts directories like /sys, /dev or/proc
　- Runs /init.rc script. The init.rc is responsible for the initial set up of the system.

Fifth, (Android) Zygote: 
　- VM process that starts as the system boots
　- app_process launces Zygote

Sixth, SystemServer
　- Load a native library called android_servers

ref. for Android: https://maoao530.github.io/2017/01/06/android-start/

refs.
https://blog.csdn.net/a4262562/article/details/76779236
https://danielmaker.github.io/blog/linux/start_kernel.html
https://cjworld1208.pixnet.net/blog/post/8014497
http://embeddedvenkatpari.blogspot.com/2016/05/how-to-load-firmware-using-pil.html?m=1
https://www.twblogs.net/a/5b8d19262b717718833b2c22
http://albert-oma.blogspot.com/2016/07/embedded-u-boot.html?m=1