A degree is not a requirement to become a professional developer, experience is. The best engineers I have ran into have been self-taught, for those that had a degree it was normally to help them get past the initial HR wall earlier in their careers.

You can gain experience as a developer by doing projects, these give you something to talk about in interviews and also count as experience. If you have no experience pick up many of the operating systems, architecture and programming books that have been highly rated in your area of interest and start reading and applying what you learn until you have a deep knowledge of the material.

An engineering manager will hire people without degrees if they show aptitude, drive, passion and have created projects in line with their missions. If you were in an interview for say a Linux kernel developer and have built several kernel modules, documentation on them, their purpose and they are very secure and stable along with being in use by people that is enough to skip to the what would you like to do here, compensation talk and when would you like to start.