serial devices on the standard freescale ubuntu build (dmesg)
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Serial: MXC Internal UART driver
mxcintuart.0: ttymxc0 at MMIO 0x53fbc000 (irq = 31) is a Freescale i.MX
mxcintuart.1: ttymxc1 at MMIO 0x53fc0000 (irq = 32) is a Freescale i.MX
mxcintuart.2: ttymxc2 at MMIO 0x5000c000 (irq = 33) is a Freescale i.MX
mxcintuart.3: ttymxc3 at MMIO 0x53ff0000 (irq = 13) is a Freescale i.MX
mxcintuart.4: ttymxc4 at MMIO 0x63f90000 (irq = 86) is a Freescale i.MX

serial devices on the linaro build (dmesg)
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imx21-uart.0: ttymxc0 at MMIO 0x53fbc000 (irq = 31) is a IMX