I love working with Raspberry Pi, so i have decided to build my custom board but with different processors as Broadcom's processors are not available in the market. Can i find the list of supported processors for Raspbian operating system ? I want to design new board in which current Raspbian OS and all its libraries are supported. Is it possible to build custom board?
Please note that raspbian.org and raspberrypi.org are different entities. The image files available on raspberrypi.org are only legal to use with official Raspberry Pi. You can use everything from raspbian.org and the Linux kernel which everybody must distribute under GPLv2 to create your "pure" variant of Raspbian, as many companies do.
Secondly it is very difficult to get hold of the Raspberry Pi SoCs. For this reason the compute module was invented. This also circumvents some software licensing issues (mentioned above), especially regarding essential Raspberry Pi firmware files.
For very serious projects, consider the element14 Customization Service. Minimum Order seems to be 5000 units (175 000 $?) but it seems very flexible and has endorsment of the Raspberry Pi founders.