How to understand the relation between LMA, VMA and FileOffset?

Below is the linker script from an ARM-based OS.

ENTRY(__entry) /*kernel entry (kernel/asm/boot.S)*/

/*kernel will be loaded at this address after boot*/
INCLUDE linker.ld

SECTIONS
{
    /*kernel will be compiled with virtual address base at 2GB*/
    . = 0x80000000 + start_address; /*2GB + start_address = (0x80010000)*/
    PROVIDE(_kernel_start = .); /*defined at kernel/include/kernel.h, set to 0x80010000*/

 .text : AT(start_address) 
    {
        *(.text)
    }

    .data : 
    { 
        *(.data) 
    }

    .bss : 
    { 
        *(.bss COMMON)
    }
    . = ALIGN(8);
    PROVIDE(_fb_start = .); 
    . += framebuffer_size;

    PROVIDE(_kernel_end = .); /*defined at kernel/include/kernel.h*/
}

It will generate an ELF file with sections like this:

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0000c610  80010000  00010000  00010000  2**2 <=== LMA and FileOffset are affected starting from this section.
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .rodata       0000037d  8001c610  0001c610  0001c610  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .data         00004000  80020000  00020000  00020000  2**14
                  CONTENTS, ALLOC, LOAD, DATA
  3 .got          00000024  80024000  00024000  00024000  2**2
                  CONTENTS, ALLOC, LOAD, DATA

I changed the linker script to below just for experiment:

ENTRY(__entry) /*kernel entry (kernel/asm/boot.S)*/

/*kernel will be loaded at this address after boot*/
INCLUDE linker.ld

SECTIONS
{
    /*kernel will be compiled with virtual address base at 2GB*/
    . = 0x80000000 + start_address; /*2GB + start_address = (0x80010000)*/
    PROVIDE(_kernel_start = .); /*defined at kernel/include/kernel.h, set to 0x80010000*/

 .text : /*AT(start_address) */ <--------------- Here Commented!
    {
        *(.text)
    }

    .data : AT(start_address) <--------------- Move it to here!
    { 
        *(.data) 
    }

    .bss : 
    { 
        *(.bss COMMON)
    }
    . = ALIGN(8);
    PROVIDE(_fb_start = .); 
    . += framebuffer_size;

    PROVIDE(_kernel_end = .); /*defined at kernel/include/kernel.h*/
}

It will generate an ELF file with sections like this:

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         0000c610  80010000  80010000  00020000  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .rodata       0000037d  8001c610  8001c610  0002c610  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .data         00004000  80020000  00010000  00010000  2**14 <=== LMA and FileOffset are affected starting from this section.
                  CONTENTS, ALLOC, LOAD, DATA
  3 .got          00000024  80024000  00014000  00014000  2**2
                  CONTENTS, ALLOC, LOAD, DATA

We can see the .text and .rodata sections LMA is not affected. Only the .data section and later sections are affected by the AT() command.

So it gives me a feeling that the VMA and LMA calculation during linking is independent of each other.

If there's no AT() command, the LMA and VMA will be the same. Once there's a AT() command, the sections that after it will be affected.

I didn't find detailed description about this behavior in the Using ld doc. Am I correct?

And why the FileOffset is also changed by the AT() command? The .text and .data sections are swapped with regard to FileOffset.