Career in Linux Internals and Embedded Systems

I am a working software professional engineer having 12+ years experience in C/C++ on Linux platform.

I have a burning desire to work on Embedded system and Linux Device Driver development - I have self practiced and learned some basics but now not sure how to proceed next. I have a PC where I have Linux OS and practice Linux Kernel development / device driver - for embedded system I self-learned 8051 and PIC16F870. But now I am hearing Raspberry PI and other new controllers would provide a good career opportunities.

If I want to pursue my career in Linux Internals / Embedded systems what things should I learn or be expertise in? I have plans to buy Raspberry PI. But I don't know what projects to practice or rather what programs to write to enlighten up. I mean I am totally confused of what I should proceed learning and development?

I need some direction on what should I practice and where I can get ideas and help of what projects to do. I do not wish to join any training institute cause they are professionals and costly. If a setup is required I would do it at my house and pursue further on.

Can anyone please guide me accordingly - like - what I should learn for better career opportunity / what projects I should self-practice and where I can get help related to projects?

For the last ten years of career I worked on an imbedded telemetry system using OS/9 (linux on a chip) as the main processor and 8051 machine interface units on a bitbus bus. The software was written by a software house. we also used Siemans control systems, again the software was written by a software house. Can you see where this is going? As I see it, there are two ways of getting into this industry the first is to work for a software house. the second is to work in some industry and become an expert in it then just buy in the software and re-configure it for this application. This second option is good for free lancing as all fruit canners will use similar canning machines, which they might want to automate. I had a friend who did just this, ran a company which at its peak employed 12 people, though due to management falling out the company was dissolved.
Frank

Getting into any company for embedded system projects just does not matches my profile - I am rejected at the basic criteria of candidate selection. Yes, I want to do some industry development project all by myself personally - but which one should I do - I get a huge list of various devices:

Raspberry PI
Arduino
Other microcontrollers
8051
PIC16F870
.........

Further I need help related to project. I am neither sure which are the best hot cakes slices in Embedded System , which will fetch me at least selected and noticed shortly.

Have you asked why you are rejected? There is no point in developing a project by and for your self unless its for bragging rights at a job interview. If you have a CV that shows you are smart, the actual devices are very secondary. We once advertised for a senior engineer and a young chap straight out of college applied, he wrote in his application that he could not do a senior engineers job, but would be willing to do any other job in our department. We got a senior engineer but we interviewed this young chap anyway. The nearest qualification he had to engineering software were Microsoft applications (but not VB!). He seemed enthusiastic so we took him on a junior engineers salary. Ten years later he is a senior engineer on about £50K.
Frank