Shader: Modify XY Position of Texture

I want to write a shader that renders textures at specific XY locations. Say there are 4 textures assigned to the shader: A, B, C, D

![acbd][1] [1]: https://i.postimg.cc/3rfVf8Wx/abcd.jpg
A, B, C, and D are all 512x512 so placed together, they make a 1024x1024 texture. However, only texture A has an origin of 0,0.
**Texture B:** Must start at 0, 512
**Texture C:** Must start at 512, 0
**Texture D:** Must start at 512, 512

How can I tell the shader to offset the origin of texture B, C, and D?