Where to start Embedded Software (other half of SOC)?

zaq.1

I have not been in the Embedded software arena till now although I have read some books not completely but I don't know which tools I need. If someone has better knowledge, can please answer my below simple question?

1- Is that OS development?

2- Is that software development?

3- Is that Micro-processor development?

4- Is that firmware development?

5- If it is all of the above, then what is the role of the hardware designer? I mean suppose you want to develope a micro-processor. Which part of it should be created by hardware designer and which part by software designer?

6- What is the role of system developer?

6- What are the best tools for Embedded softwares?

7- And anything that can help?