doubt about where to put pin-mux in MX28 based platform DT

[Hector Palacios]

Hello,

I'm creating the DT for a custom platform based on Freescale MX28 CPU and I have some 
doubts about where to add some pin mux configurations: whether in imx28.dtsi or in my 
platform dts.

A pair of examples folow:

Example #1. My platform is using a valid IOMUX for DUART TX/RX lines which is not 
covered in imx28.dtsi, namely the I2C0 pins. Since this is a valid IOMUX that can be 
used by other platforms, I'd say I should included it in imx28.dtsi:

diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
index 3fa6d19..8928b7b 100644
--- a/arch/arm/boot/dts/imx28.dtsi
+++ b/arch/arm/boot/dts/imx28.dtsi
@@ -186,6 +186,17 @@
                                         fsl,pull-up = <0>;
                                 };

+                               duart_pins_c: duart at 2 {
+                                       reg = <2>;
+                                       fsl,pinmux-ids = <
+                                               0x3182 /* MX28_PAD_I2C0_SCL__DUART_RX */
+                                               0x3192 /* MX28_PAD_I2C0_SDA__DUART_TX */
+                                       >;
+                                       fsl,drive-strength = <0>;
+                                       fsl,voltage = <1>;
+                                       fsl,pull-up = <0>;
+                               };
+
                                 duart_4pins_a: duart-4pins at 0 {
                                         reg = <0>;
                                         fsl,pinmux-ids = <

Example #2. My platform assembles a NAND chip which is powered at 1.8V. The imx28.dtsi 
has a configuration 'gpmi_pins_a: gpmi-nand at 0' that configures the pins at 3.3V.
Should I create another entry here 'gpmi_pins_b: gpmi-nand at 1' with fsl,voltage = <0>; 
or should I create a specific entry in my platform's DT instead?
What is the convention?
-- 
Héctor Palacios