where is the syntax for .sct (scatter file content) defined? Did ARM originate this file type?

Automatically generated when I create a new project with Keil: my.sct LR_IROM1 0x00400000 0x00020000  {    ; load region size_region   ER_IROM1 0x00400000 0x00020000  {  ; load address = execution address